I think that for Soviets especially, but also possibly for USF and OKW, you need to be careful with this. Soviets are not designed to get all 4 tiers, so saying that Guards only come with a T1 limits strategies. This would be extra punishing for call in tanks, as both Soviet T3 and T4 cost 120 fuel, meaning you couldn't use T-34/85s with SU-85 back up or an ISU with T-34/76s.
USF is also encouraged to tier skip, getting either Lieutenant or Captain. Thus stuff like Paratroopers, Greyhounds, or Wolverines should be either have Lieutenant or Captain + CP gate.
OKW can skip tiers, but they generally seem to get all 3 in a game. Their tech is also the cheapest.
No one said you cant go T1,get guards and M3,and then go t2 and lock down the territory you took with Maxims, as sovs,its just not always viable since it costs too much
Conversely,no one said you couldnt go T2 and get Maxims and shocks,and then turn around and throw those shocks in an M3.
T34/85 could be put in T4 too,i was just throwing ideas around.
For the Soviets they
should definitely implement cheapened teching each time you build a new building.(Cheaper T2 after T1 for example) to increase the amount of strategies you can screw around with,which would change the spamness of the sovs forever.
Most callin inf doc besides the soviets would remain unchanged. Paras could still drop regardless of your tech,pathfinders would still pathfind at 1cp,etc etc.
Greyhound would probably require LT and 3cp.(Which means it would be relatively unchanged.)
Assault Grens would be the same as ass engineers.
Also for the Okw,Jagdtiger comes from flaktruck,after all 3 buildings. No more 24 min jagdtigers..