Yeah, that leaves Guards and Conscripts. Quite the pickle really, the entire Soviet faction needs to be torn apart for a true 1941 faction.
I think, in this case, USSR should have liner upgrade system, like OST, with core guards in T2 or T3, and non doctrinal T-34 with KT access model or after expensive upgrade in T3/T4.
T0 - eng, conscripts.
T1 - maxim, mortar, snipers.
T2 - something from BA series, guards, AT gun 53-K (it's easy to make it, it's M-42 with shorter barrel)
, Zis 3 with upgrade to med truck.
T3 - BT-7, maybe GAZ truck with AA
, upgrade for T-34 production.
or
T4 - T-26, ZIS-30 or just ZIS-2 AT gun
BM-8-36
KV-1 and KV-2 doctrinal, most expensive and armoured tanks in the mod, shocks are changed to 6 cons/guards with PPSH and smoke but without armour.