I would debate a bit on the choice of firearms.

The PPSh was chosen for mass production for its simplicity, good-enough reliability, and shocking firepower at close range.

The SVT-40 was a good one but it required some decent skills to maintain it in the field. And most Soviet conscripts were still not technically literate enough to maintain it properly. That's why it fared badly in conscripts' arms (and good enough in everyone else's) and thus phased out.

The Simonov carbine (the SKS) was a good compromise for that case.

So I would suggest this line of development:
WWI: Mosin;
Interwar: Tokarev SVT-38 or SVT-40 (or keep at tier 3 for marines, paratroopers, mot/mech etc);
SMG: Shpagin PPSh;
Semiauto: Simonov SKS
Assault rilfe: Kalashnikov AK*

*not AK-47, please, just don't call it that way - in MOST official docs it is simply AK. AK46 (AK-46), AK47 (AK-47) are mostly applied for the prototypes and pre-production series.
For that case PPSh-41, SVT-38, SVT-40 are also "popular (and mostly modern)" nicknames. Because these were actual given long boring names and shortened to names like PPSh, TT, SVT, DP, PPS (sometimes adding "obr. 1941" or "obr. 41" and the like, i.e. "pattern '41", after them).

P.S. If you can add visuals for shock troops the ShISBr guys (Assault Engineer-Sapper Brigades) (those guys with cuirasses and top weaponry) are just great for that!

Overall great work, but I wish that either the Tier 0 or Tier 1 Infantry used a pilotka rather than a helmet, just feels like that would be more recognizable than the Adrian or the SSh-36

Pretty sure the VDV (Airborne) wore brown side-caps in WW2. The last tier model could probably have the standard SSh-40 helmet that's already in the mod.

Today they use a light-blue beret, in case you wanna skip modelling a side-cap and use the marine cap.

I agree with what a few others say, a Pilotka would be more fitting for the Tier 0 and Tier 1 infantry

Do a Soviet paratrooper uniform please.