There are a few Ostheer concepts that name Panzer III as the Ostheer "MBT". It's fast, it's cheap, and it can still stand up to Soviet tanks. Could also be an option.
The Panzer III could stand up to a BT-7. It was effectively a light tank. The Panzer III was used to combat T-34s in the early goings because it was literally all the Germans had initially to combat the T-34, seeing as the Panzer IVs for the invasion were Ausf. F1, which were almost completely incapable of destroying enemy armour. The truth is, until the Panzer IV Ausf. F2 arrived, the majority of T-34 kills were made by anti-tank guns, particularily truck-towed 88mm AA/AT guns.
if i ever make an ostheer concept i would have the Panzer 3, which can upgrade its shorter 50mm gun to an L/60 gun (Ausf J upgrade) for more anti vehicile firepower at the cost of anti inf firepower. (also, it would gain a bit more armor and side skirts.) And once Ausf J upgrade is complete, PZ3 can use APCR rounds abilityfor 50 ammo, where it gains much better penetration for about 3-4 shots. Also, Stug III would be anti infantry role, more effective then Stug 4 versus infantry, but crap vs tanks. It could, however, fire a single HEAT round for 40 ammo, that does heavy damage to vehicles and pretty good vs tanks. However, at another tier on, Stug III's gain individual upgrade to KWK 40 L48 gun, giving slightly greater anti tank firepower then stug 4, but losing HEAT round ability, and becoming worse vs infantry then unupgraded stug3. Jadgpanzer 4 would be late game TD, starting with Hetzer PAk 39, then being able to upgrade to KWK 42, slightly better then panthers gun. Also, i suggest Panzer 1 as early game anti infantry. It would be doctrinal 2 point call in, and be armed with 2 bunker Mg42, with heavy supression and firepower. However, it isint the fastest light tank, and altho immune to bullets, 2 PTRD rounds or one hand grenade or one shell of any kind will instantly destroy it.
Late in the war thry stoped makeing panzer 2s,so it become uncomman.