4vs4 would be easy enough with the CinC having forces to command. That is what the midnight transfers are for. IMO, transfers should be anytime. Players would also have to understand that at any time they would control more or less forces as the situation dictates. The CinC should have some forces to command because that keeps him from getting bored.
If you need two people to withdraw, I'll be one to make it easier to get going. You can keep me in mind as an alternate in case somebody has to drop out.