It seems, at least to me, that there would be substantial benefit in allowing users to add questions to Area51 proposals after the proposal is in the commit stage. Not only does it mean that the question has a higher likelihood of being answered (It means it is immediately available when the board starts, day one, instead of requiring the user to wait until the commitment stage is over), a boon for the user, it also means that the board has a high likelihood of participation in its very first days (more questions = more potential user interaction = better). For that matter, it is also quite possible that someone might come along and want to ask the best question on the topic, EVER (you know, something on the order of "what is 6 times 9?"), but they would not be allowed to because of the "no questions while committing" policy.
(Forgive me if this is asked and answered, I will gladly delete it).