A whole month of delay, great. But I made it. Almost. The storyline for the HRE ended up being a bit longer than the Orthodox one, which itself was supposed to be a prototype storyline for this one — the base of the storyline is actually similar:
Baptism, 'one major point', unification of the Western Slavs; additionally, after choosing the province branch, further decisions appear regarding the creation/reform of the HRE, creation of new imperial kingdoms, and the proclamation of the Imperium Universalis.

The length itself wouldn't be a big problem — the problem turned out to be coding a few ideas I had, because of how unfamiliar this was for me etc. — not to mention the lack of free time after the end of my days off. Anyway, the update is 99% ready, I literally have one last thing to add, a few copy-paste decisions for the 'epilogue', but there are quite a lot of them (tedious work) and I might not make them in 2 days — and then the update will be delayed by a whole week again, because I have a trip. That's why of two evils I'd rather release finally now and simply add this ending later — especially since this update will be fully compatible with games that have already started.

• Added a storyline for Roman Catholic Poland (in both 867 and 1066).
  
• Changed names: Stodorania → Morizania, Eastern Roman Empire of Slavs → Eastern Empire of Slavs and Romans, Latvia → Lethia, and in 867: Kuyavia → Goplania and the kingdom Goplania → Goplia. Polabia got German name Ostmark.
  
• Changes in the colors of the kingdoms: Polabia, Pomerania, Transdanubia, Carinthia and Lethia.
  
• New duchy de jure for Transdanubia and in 867: new duchy in Eastern Silesia (and Silesia got Brzeg county).
  
• Code fixes:
  
• new Polish cultural title names were encoded using the localization, not directly in the landed titles file;
  
• the last ruler to convert to Orthodoxy wasn't shown in the Mend the Slavonic Christianity decision;
  
• required controlled region for the Voivodeships' Fragmentation decision (now it uses a geographic region, not the kingdom one), also fixes the problem that the confirmation button was unclickable;
  
• names for feudalized tribes in 1066 (Głubczycans and Opolans);
  
• de jure kingdoms in Empire of Slavia (sic.) depends on the creation of the Polish provinces (kingdoms removed from the map are no longer de jure part of the empire).
  
• Changed the name of the By the Grace of God Kings of the Poles modifier → Kings by the Grace of God.
  
• In the The Rise of "Poland"? event, Szczerbiec is given.
  
• Płock Diadem (version for the empire) has an increased vassal limit 10 → 15.
  
• When the emperor is Polish, all vassal kingdoms change their name to Provinces and instead of kings they are ruled by Viceroys.
  
• Piasts gets the historical motto of the First Polish Republic.
  
• The Greek customs? event now takes the expansion into account.
  
• Havelians have the duchy title back in 867.
  
• Historical elaboration of some events (including Orthodox ones).
  
• New pictures for decisions.

• Update of the mod to 1.16 game version.
  
• Change of Polish names of a few titles of non-De Jure Kingom of Poland
  
• Change of Polish and Polabian names of: Sorbia → Serbia and Sakskia → Stodorania. Polabia's titles will be reorganized in the Pagan Update anyway...

About the fact that Reform Voivodeships' Fragmentation decision is unclickable — it will be fixed in the next update. For now, to make it clickable again, temporarily set GUI scale (settings, graphic) to 90%.

• Game is translated to Polish. Finally!
  
• Name of Głubczycan's formed Poland is renamed: Brzegiap/i] → Gubczyciap
  
• Localization fixes

Damn, 3 months since last update, and I'm coming just with this? Sadly, starting working took my way too much free time, so I can't really work on my mod properly, not to mention my technical issues. I'm not making myself excuses, just when I had free time, I could do, what I feel like to — now it's just Saturdays really. Not to mention little burnout itself, and I work alone on this. Though seeing that people actually like my mod, I'll try to resume my works. Knowing though my slippery feeling of time, I will fix my laptop by the end of this month (so will be able to work on CK properly) and as for the free time, I will have longer break by beginning of May (so I will be able to do the update all at once — I very dislike working on it in small bits, hour or two per day), so sth like, by half of May a bigger update should come up (in theory it will be the Roman Catholic update)

• Now, when the player becomes is any way emperor of the Eastern Roman Empire in the province branch, two events pops up: First for deciding whether it's time for Polish imperialism, Slavic imperialism or strengthening bonds with Greeks, second about possibilty of assimilation of some Greek traditions. It ain't much, but it's honest work.
  
• Localisation. Among others, historical description of Voivodeships' Fragmentation was extended.
  
• Regions of West Slavia and Slavia are fixed again. For some reason each game update breaks it and I have no idea, why.
  
• Balance: vassalising through Orthodox character interactions is more expensive now again. In addition there were added the same AI modifiers that are present with standard vassalisation — they are not as harsh though as there's +25 bonus (it also applies to Orthodox converting a neighbour ruler).
  
• Fixed lack of appearance of specific decisions (both in 1066 and for non-Poles in 867).
  
• Also forming Mińsk Voivodeship was fixed (decision was checking wrong counties in effects).
  
• Now specific counties (specifically their tier names), when held by Poles, are named not Powiat, but Ziemia instead (according to historical administrative division).
  
• Adjustements around the forming new provinces at the end of New Voivodeships: ... Province: now you can revoke with character interaction a province from a ruler, so it's easier to handle (they are just governors after all), also splendor multiplier has been fixed as well (it turned out that every living dynasty member had +15% bonus...).
  
• Sandomierz is back under Polish rule in 1066.
  
• Spisz Voivodeship is no more, now the county is part of Kraków Voivodeship (it's much more historically accurate).
  
• Polabians now have Bellicose ethos.

• Game has been updated to the Basileus update

It is a pre-update before the DLC. Just in case I want to split the update into two: new stuff and new game version update, have bad experience with merging these two,. I'm also planning at least one content update for the Orthodox storyline that would expand the province branch (it depends on how will the new update/dlc looks like, but regardless that for 99% I will do something). Then I will focus on the Roman Catholic update, yet there are no dates for the 1.2.2, let alone the 1.3 game version.

• Vistulians now start with a duchy title.
  
• Localization again.
  
• Polabian duchies if held by Poles, have Polabian names. Further work on that will have place in the Pagan update most probably, now I only changed the most noticeable thing.
  
• Rework of Orthodox vassalisation interactions — more patched unexpected situations and requirements are now harder to meet, but also interactions are cheaper to enact. We'll see, how will it work like that. Possibly there will be a nerf in future update, who knows.
  
• New Polish voivodeships now have standard names (Poznań Voivodeship → Voivodeship of Poznań etc.) to fit all the other duchy-tier titles. Also when establishing Voivodeship of Pomerania, now Kołobrzeg becomes part of Pomerelia instead of Słupsk drifting to (proper) Pomerania.
  
• Update of code of establishing further new voivodeships — now you actually pay for the title, not secretly send money to some other people (I got confused with wording of the code).
  
• Now when West Slavs are unified by Orthodox ruler (either independent or province branch), he or she is gifted by the Byzantine emperor with a valuable and useful diadem with its own model. Depending on the branch, it has different effects.
  
• Modification of Lechitic cultures (traditions) now is moved to on_action. For some reason previously opinion modifiers weren't working for the cultures, now they do.
  
• When fervor penalty is applied at Roman Catholicism when Slavonic Christianity is mended, now Orthodoxy gets fervor boost for the same reason as well.
  
• The ruler, who unified the West Slavs, is now know as the Restorer, not the Wend. It more fits the Christian world + one of Polish kings actually had such nickname

• New flavour Orthodox events got edited and extended (both in terms of localisation and now some events and interactions give legitimacy), got some ideas in bed + other small changes in localisation of the new content.
  
• Tweaks of code of decision Unite the West Slavs (in the Province branch): now if you are empreror and have kings as vassals, they will not go independent anymore, every held empire title is getting destroyed (previously only the West Slavic ones were scoped), Country of Kran stays in Kingdom of Sklabonia (previously entire Duchy of Philippopolis was becoming de jure part of Kingdom of Thessalonika, because of Greek majority. Now the Bulgarian borderlands stays in Duchy of Moesia).
  
• Little tweak of decisions New Voivodeships: ... Province — now creating new voivodeships (this doesn't apply when making voivodeships bigger, like Ruthenian or Poznań) both costs gold and gives prestige and legitimacy.
  
• I have no idea, what to think of this (if Paradox did that on purpose, or just messed up, when adding new scripts), but I 'fixed' a problem that when destroying titles (in-code, like during unifications or establishing new voivodeships), the character was loosing legitimacy. It's not happening anymore within the mod's content.
  
• Changed capitals for tribes (so names of the tribes and their capital counties are matching): Hevellians, Redarians and Reregians. Also Hevellians eventually lost their duchy title (since not having more that 50% required lands to form the duchy). About the duchy, it was supposed to work since 1.1.1, but just now I found that it wasn't.

• Day one patch, yay! Fixed trait triggers in character interactions

• Added small storyline for Orthodox Poland (in 867) with two endings (independent empire or province of Byzantine Empire). It ain't much, but it's honest work.
  
• Little rework of the event Baptism of Poland (text and coding) like adding info about Orthodox beginings, fixed mistaking Krstjani with Slavonic Orthodoxy, making Vistulians convert to Orthodoxy (when AI) or adding notification: Recommended choice for this tribe (such choice results with getting small amount of legitimacy).
  
• Goplans tribe now hold Duchy of Kuyavia at game start, since, most probably, they subjugated Polans — they earned it then lol.
  
• In events that contain historical informations, fictional part that refers to your game is now bold. It should make them more appealing, I guess.
  
• Little changes in localisation (fixes, fixes... And improvements of formatting).
  
• Little tweaks in the Lech and Czech bookmark (it was renamed + mainly was tweaked the tab of Lendians).
  
• Establishing Most Serene Kingdom of Poland (event) gives legitimacy and more splendor than before.

• About forming Empire of Sclavinia as Orthodox Poland, there are two ways of doing that (story branches): establishing new Slavonic empire (standard Unite the West Slavs way, nothing really new here except renaming Sclavinia to Greek Sklabonia) or introducing Byzantine Empire to the (Holy Roman) idea of Imperium Universalis (alternative way that unites West and South Slavs within a de jure kingdom-province of Byzantine Empire). The storyline adds basically one major point between forming Kingdom of Poland and forming Empire of Sclavinia, with addition of new character interactions. I tried to make them balanced, but I didn't test that xD I will check that though on my own really soon, so possibly there will be balancing in future. Otherwise this update would be postponed even more.
  
• This storyline is also a forecast of Roman Catholic update, that would empasis much more on realisation of the Holy Roman Imperium Universalis (this idea was utilised for Byzantine Empire in this update) — it will be much more than just becoming a vassal (like it is in the Orthodox storyline).
  
• Possibly I will enhance the Orthodox storyline though (specifically the province branch) when the new DLC will be released (depeneding on how it will change Byzantine Empire).
  
• In the province branch, for now I decided to hide the decision Unite the Slavs, because I have no idea, how to make it balanced and just properly work within the setting. Making one huge kingdom from territories of 3 empires would be just grotesque, splitting territory of Empire of Slavia into two kingdoms (East Slavs being united into Kingdom of Antia + West and South Slavs within Kingdom of Sklabonia) is counterproductive, because the unification doesn't unify all the Slavdom in that case + even if the player would become king of these two kingdoms, Antia (or Sklabonia) would be lost under succesion, so what's the point? Unless I in addition change succesion to primogeniture, which will be insanely OP that early. If you have any suggestions, how to handle that, please comment!