1) To pull of a system like this would definitely require pre-arranging everything with a staff set, and we don't have that.
2) Most of our helpers are also participants in the majority of events. How can they scramble for other events when they're competing?
3) Most people are competing in multiple events; how can you submit a puzzle in advance when you're busy competing in a current event?
4) It would be naive of us to expect to rely on people to hand in puzzles in advance as people are generally unreliable.
I'm not saying it would be impossible, it would just require a level of preparation and complexity that isn't worth the hassle for what would probably be minimum benefit. Personally I think it is a good idea to have a few minutes with that transition between events. Also, usually there are one or two stragglers that we end up waiting for to finish, and while they're finishing we're making a headstart on scrambling for the next event anyway.