this is what I envision for the system:
game ends, we take a day or two break, gives people time to add/drop. We (mafioso) then decided which game is going next based on how many people are in the queue (assuming we have enough to fire a game). We announce the game that's going next, and host puts up their rules and a tentitive start time. We then give another day or so for the host to get his shit together and for people to add/drop based on the new game, then fire it (assuming the host doesn't need more time or want to start immediantly).
that would cover your concerns because it would give people time to drop in/out based on if they like the rules or not.
The current system isn't broken, but it is certainly way clunkier than we would like. There's no reason not to try a new system, this is a trial, worst case we can just revert to the current system.