Just throwing this out there.
I think the stug in it's current iteration could fit in t2 quite easily.
It's quite vulnerable to infantry, and doesn't have much damage potential anyways.
Light vehicles can outmanuver them quite well, but the stug in that phase gives OST a fighting chance while opening up an easier path to t4.
Historically it's a infantry support vehicle, and so it would make more sense in the infantry heavy phase of the game than in the armored.
Stug in t2? Then it will become a 120 damage per shot unit with 400 hp like su76. And for balance fuel cost decrease to 70 lol