You cant look at OKW, this comparison cant be more wrong really. OKW got tech changes not to provide you with full access to backtech tier, but to give you access to medics, since its a basic tool, which never should have been locked behind chose. You still have to pay just as much, if you decide to fully unlock med track units.
So are things like an AT Gun or MG are not a basic tool? Soviet T1 ends up giving up any form of support weapons until they do a very expensive back tech (in terms of how Soviet tech is set up). OKW for comparison is always gonna have access to both their MG and AT throughout the game so the backtech for medics/ISG is now even easier and isn't as pressing an issue. A soviet backtech to T2 essentially just gives them access to everything the OKW would get just in a different way. OKW backtechs for Medics and ISG while SOviets have to back tech for AT Guns, MGs, and the mortar. I would say AT Guns are much more important to have than medics in the late game yet the Soviets have a bigger cost to backtech for them
Right now soviet T1 and T2 in their core idea, arent meant to be used at the same time without any resource punishment.
In its core this idea that "Either T1 or T2" is the opened pandora box. Because idealy both T1 and T2 units should justify skipping each other, and they are by far dont, well T1 at least. Because in any case, if you are unable to roflstomp your opponent with T1 and force him to surrender and completly baselock him, you will still need T2 at least for an AT gun.
Personnaly I think this is over-all bad desing, and T3 should requare both T1 and T2 to be build, with proper cost ajustment ofcourse. In this case at least whole soviet T1\T2 units can be balanced in context that you will always have access to them, because they are part of your tech and not self sufficient buildings, which ideally should provide whole roster of self-sufficient units.
Regardless of whether it's bad design or not it is what we have to work with. You just can't make T1 viable unless at some point you make it easier to get stuff like AT Guns. PTRS rifles just won't ever measure up to an AT gun in how it tackles mediums and up. I mainly want to just make it easier late game for Soviet T1 to get access to AT guns late game when they really need them. There is still a pretty big gap where the Soviet T1 wouldn't have access to AT guns with a change like this and the Zis Guns wouldn't even have any vet.
As I've said again and again without giving T1 viable AT in some way your just not going to see it work. I guess if you want to power up PTRS further in some way that could be an option? Like split up the PTRS upgrades so Penals get 2 for the early game and then go to like 4 late game? I personally prefer just letting Soviets backtech for a discount once they get T4. Seems easier to implement and shouldn't cause that many balance issues.