making the Brets use normal BP would tilt the balans the other way, loads of easy units to score for opponent.
We played several variations of rules on multiplayer, most obvious one is that have allies leave the field, and the variations you mention could both work.
Alternative sollutions used,
break off all allies CHARACTERS, which will allow you the troops on the field but forces you to spread command
drop allied commanddistance to 20cm after they reach BP
Andof course, you COULD opt to use an objective driven game, instead of basic WM end°of°game