I've seen many fantastic questions in proposals that wound up lost when the proposal was deleted (such as due to inactivity). Often only to see the concept restarted with a new name, perhaps a slightly adjusted topic area, and then eventually succeed.
I'm involved with quite a few proposals which are borderline for getting started, and believe they'll eventually come about. I don't mind at all repeating the work to try to get followers and activity... but the disappointing part is the time put into coming up with unique and interesting questions. Certainly no qualms on not allowing them to be answered until the site makes Beta, but the questions to me seem to often be like wrapped gifts waiting for the morning when they can be finally opened; the proposed questions often are much of what draws me in to commit to a proposal, when they show just how interesting the questions can be. Yet they get lost to the abyss.
Could we get some way to at least keep our own posted questions, if not also a list of other questions we had interest in? It could be stack exchange wide, a text only list of posted questions that have been deleted. Or it could be somewhere here. I agree we don't want to overly encourage just regurgitating questions when a proposal restarts... but it's also a real pity to lose some absolutely fantastic questions.