I agree; people should have their setups ready prior to the game before theirs ending, though at the very least it would be awesome if people finished their setups prior to closing sign-ups. There's always a delay between sign-ups ready and game starting due to people "still needing to write role PMs" or "need to review setup". There's a long, long time inbetween your sign up to host a game and actually having the chance to host said game. It's a bit silly people wait until the very last moment to prepare their setups.
So yes, I vote in favour of making it mandatory that people have their shit together when it's their turn, in addition to requiring every mod to state plainly and clearly whether their game is bastard mod or not, if need be by defining what "bastard mod" means.