Combine Grey Knights, Inquistators and Sisters into one faction?

[Quasicide]

The faction polls made me realize two things: there are a lot of great 40K armies, and most of those factions are never going to make it into Gladius.

So I found myself wondering, could you combine Grey Knights, Inquistators and Sisters of Battle into a single Inquistion faction? Would that give the faction wider appeal? Or would it just be raving warpborn madness and I should report to my local Commissar for purging?

[Chameon]

So, Slitherine has indicated they're going to be sticking to the books lines I -believe- (Although I did not save the quote, and even if I had very little stops them from changng that), so no Daemons/CSM (Much as I would -revel- in that), and no Sororitas/GK/Inq, and no GS Cultists/Nids, and etc etc.

This means that the game is unlikely to mix and match factions.

Now, as for mixing Inquisitors, Sisters of Battle, and GK into a single faction, it's honestly -semi- reasonable. This planet has a lot of canonical reasons (Especially when Chaos shows up) to have Inquisition interest from all quarters, Ordo Xenos already has their reason, the Ad Mechs were messing with nids there, so they -clearly- want to keep attention, but that would only explain Deathwatch, which, Deathwatch is not GK or Sisters. Ordo Hereticus sorta lightly has their fingers in all the pies in the galaxy, so they could be explained as having a presence there, and thus they could -probably- control the local sisters, or perhaps the lord inquisitor even has their own personal coven they've more or less hijacked to slaughter unbelievers.

That leaves the Ordo Malleus. Which is awkward. Y'see, the Ordo Malleus is technically distinct from the Ordo Hereticus, which means their fingers tend not to be in as many pies internally. While theoretically they're supposed to look inward, as most inquisitors do, the Ordo Malleus has this tendency of, if there's not a prophecy about it, they tend to focus more on either things that have already happened, or on things that are outside of the Imperium. They're best thought of as weaker Space Marines, to be honest, as they tend to eventually get Terminator Armor and then just start trying to hunt down Daemonic Incursions. So basically the only time when the Ordo Malleus would show up...stuff would already be going down, unless they explained this place as having some sort of ♥♥♥♥♥♥♥♥ prophecy, and the Ordo Malleus would be responsible for the strong arm of the GK.

Here's the lore issue with having some sort of ♥♥♥♥♥♥♥♥ prophecy, though. If there's crazy ♥♥♥♥ -destined- to go down on this planet on a daemonic level, and they're 99% certain it's going down here (Or...in some Inq's case, 20%), then why would they have all this other stuff set up around the planet? Why would they have a container of Nids? Why would they risk all the different things that could go wrong? Why HERE? Everything they have set up that's sensitive, they might as well migrate elsewhere, as they could probably pull out reasonable Inquisition explanations ("Get out or I blow up your facility on this planet...") to kick people off, and Ordo Malleus tends to be about as subtle as a sledgehammer with their 'requests.'

THAT HAVING BEEN SAID, while the lore for -why- all of those forces are working together would be a bit weak, you could also explain it as the Ordo Malleus just joining up because of similar doctrines, which isn't that difficult ("Oh, you're a member of the Thorian faction? Hah! So am I, let's team!"), and that could -reasonably- explain why they've got GK on call, distantly. That said, at that point, you're basically making a power armor evolution race. You go from Storm Troopers, into Sisters of Battle, into GK, into GK terminators, basically making you have slightly better Space Marine infantry, but slightly later, and you vehicles-wise you go from Sisters of Battle flamer-vehicles, into sisters dreadnoughts, into arty, into GK Not-Dreadnought Dreadnoughts.

Overall, I think it would be a bit of a mess of a faction, because while it could be done, it runs into a few consistency issues. I think a more sensible stroke would be Inquisition/Sisters of Battle, giving the Sisters some of their faith abilities, and leaving GK as their own faction, because frankly, it lets them both maintain their own identity, and it doesn't have you having to desparately shoehorn in Ordo Malleus showing up, you can have the GK be separate enough from the Ordo Xenos that they didn't even -know- about the Nids/etc until they were basically planetside.

edit: Replaced doing with changing in first paragraph.

[Quasicide]

That's a very well thought out and comprehensive answer.
You've convinced me, thank you!

[Chameon]

Not a problem, it was a fun question to answer, thanks for asking it.