Good feedback, thanks!
A mystery-oriented theme is a good idea! I just put those there since someone said they like having optional themes just in case they can't think of anything, to get them going. But that is a good "this jam only" focusing idea.
I think I may loosen the rules though some folks love them -- or have "styles" of jam like the Ludum Dare's compo vs normal entry. Also I may add more of the intended support routines (I cut 4-5 due to time).