it could be a volley kind of thing. such as
team A: 1 and 2
team B: 3 and 4
1 goes first, then 3, then 2, then 4, repeat.
its a good way to ensure you dont take MASSIVE chunks out of your opponents health early on. 3 could activate a defencive card, so 2 doesnt pull a dragon first turn (yes, it would be possible in team duels [mono towers]) this system is pretty balanced and should work quite effectively. please tell me if you find something wrong with it.