The PPsh upgrade does need any buff it was dominant when buffed last time and suffers ony from power creep (see SVT).
It's not powercreep, it's just not good value and comes later compared to CQC options of similar strength of other factions.
At most you could remove the PPSH upgrade from Guard Rifle Combined and only keep hit the dirt, cause that's already a top 5 commander that doesn't really need CQC infantry on top of elite long range infantry. The other PPSH commanders aren't nearly as good in comparison.
replace m5 with m3 lower cost
An M3 at this timing would be useless. You can upgrade the M5 with the Quad so it can grind stuff at long range, you don't want to be doing drive-bys at 3 CP (the 7 to 8 minute mark).
Maybe if you reduced it to 2 CP and replaced the M5 with USF Mechanized's Assault M3, I don't see a need for it though.
Vehicle detection is a weak ability but the ISU is one of the most powerful super heavies so the rest of the abilities should weaker.
Zis truck is NO form me for reason above.
While I agree IL-2 bombing strike should be replaced as well, vehicle detection is the most useless ability I can think of in the Soviet ability roster. If Vehicle Detection is kept, it should be an ability available to every infantry squad individually and only cost 15 munitions to activate like on PTRS Conscripts and AT-Rifle Sections (cost should be lowered on Schreck Storms as well).
Anyway, a supply truck really wouldn't be that strong outside of 1v1, because resources aren't shared. An exception maybe maps with a very safe fuel, which aren't common.
No to B4 and to ML20. The commander is AT themed and AI units do not fit.
B-4 is AT themed, or it wouldn't do 640 damage (or 480 + stun as I suggested). I can find you plenty of compilations of B-4's killing vehicles.
Generally speaking Soviet commanders have some abilities that exist in many commander and some that are available to few commanders. Imo one should reduce the number of very common abilities and increase the number of more rare abilities. Some abilities like "tank hunter ambush" should remain "trade mark" to commanders.
This sounds contradictory: reducing the number of common abilities, while increasing the number of rare abilities. You'd have to design a lot of new abilities if you want to accomplish that.
I tried to keep it reasonably simple with 1 ability swap max and creating new abilities only if the assets already exist (ZiS supply truck and smoke drop would be reasonably easy to add).