Following-up this other discussion:
Why would I want to "keep track" of all of the questions I have asked as samples elsewhere when I do not have to do that for any other SE site? Questions shouldn't "go away" if/when a proposal is marked inactive.
Marking a proposal inactive and putting it in a different view (one wherein users who hadn't noticed it go inactive could reactivate it with some threshold of activity) rather than being deleted.
The only proposals which should be deleted are those which are blatant duplicates, or ones that have been on the "inactive" panel for, say, 3 or more months. And even then, the questions submitted to the now-defunct proposals should be kept attached to the user's account - perhaps migrated to an "orphaned questions" tab for the individual user so they can reattach/reask them to a better/new proposal if/when the time comes.