No Offence intented - If they join your Team making it unbalanced, why dont you switch over?
I know i prefer being Allied as well because i prefer attacking but if its uneven i switch anyway, since it will make the Game more enjoyable for everyone.
Its just an ongoing thing which we cant do nothing about when no Member is on the Server, but the Regulars themselfs can do something about it.
The Bots cant be set up this Way that they leave like this.
They only leave when 12 Players are playing and replace them.