All for it.
Two platoons of four?
Depends on nation doctrine established by host. For example eastern block countries like the USSR operate tanks with platoons of 3 while USA operates tank platoons of 4. In some cases like in world war 2 they were tank platoons of 5. All platoons will operate under a company which for this case I recommend 3-4 platoons. A light tank platoon, Two medium tank platoons, and a heavy tank platoon.
Now as for everyone having to use the same tank, I mean that everyone in that platoon has to use the same tank. If the platoon commander has a Tiger I, then everyone has to use Tigers. If everyone has Panzer IVs Ausf.H, then everyone has to use Panzer IVs Ausf.H. Etc, Etc, Etc.
Each platoon should be lead by a trust worthy player/mod/and or host. If need be, the platoon leader can be an NPC.