The M20 would only be reliable from the rear and bazooka on LT would be mandatory.
USF needs the Initial fuel cost of its buildings lowered and added onto the secondary Vehicle upgrade so that they can get easier access to AT guns (which is why Airborne is so strong, you can skip the fuel cost of tech to get both .50 cal and At Gun) but anyway that has been spoken to death about USF needing a rework.
If it comes to late it would be a pain to get the 250 to VET1 so that it could reinforce.
The Infantry halftrack doesn't need to be a copy and paste of the Whermacht version, just like how the P4 is different in both factions the Infantry Halftrack can be different as well. If it could reinforce from the start, and have its MG upgrade locked either behind vet or with an ammo upgrade (it would have shared vet like kubel) it would be fine. Would need some tweaking for sure.
To get back on topic though with Penals, I have always been against Penals being a main part of the Soviet unit as it doesn't make much sense thematically. I would swap Penals and Guards, even if they are functionally the same with same stats and what not just for the thematic point of view it would make make way more sense for Penals to be doctrinal. One of the biggest immersion breakers in COH2 for sure is having an army entirely of "criminals" instead of honorable soldiers.
Imagine if Relic took Grenadiers and swapped them out with Ostruppen. It would be equally as stupid having doctrinal Grenadiers.
One thing that Soviets do need for its Infantry is to smooth out the veterancy. Like they are complete shit and then once Vet 3 hits they get all the godly buffs for example conscripts gain roughly 30% -received accuracy at vet 3. Instead of such a large improvement it should be split across each vet level. So in this example 10% for each veterancy level to smooth it out. They would end up being the same vet 3 as they were before but you wouldn't see such dramatic shifts in performance due to losing a squad making wipes less punishing. Wipes on Soviet units especially Penals are extremely brutal due to lack of upgrades to carry them.
Like for Grenadiers or Obersoldaten for example, you wipe a squad which sucks but its not as big a deal due to most of the power of these units coming from Mg-34/Mg-42. They can still kick ass without Vet.
Soviet units without Vet suck complete balls due to all of their power being in Vet 3.
With the Veterancy smoothed out Penals would be in a much better spot.