I like 2Flex-2-2. It covers every composition besides SoloTank/SoloHeal. And you could unlock that option with either 3 or 4 votes. Depending on the Role Picking method used.
✅ [Role Select] Finalizing this concept
Realistically 3-3 should be solved through balance. (i.e. Brig)
🐐[GOATs] Easy way to fix it