The system should be able to handle switching the start and end date of a jam a bit better. Right now it's technically possible to host another instance of the same jam this way, but it introduces some problems, namely the fact that when ratings are open after the jam, it opens up ratings for all games submitted, including the ones that were for a different jam.

If you're making the successor to a jam you previously hosted then I recommend creating a brand new page. The jam pages aren't really designed with opening up submissions again in mind. Does that work for you?