The boss stages could use a bit of variety, especially considering that they're farmed all the time.
What I'm suggesting is that you create another set of levels leading up to each boss, and then put them in the level rotation. So I'll have a 50/50 shot at getting into each pair of FSC levels. Maybe instead of the bridge level make a backdoor entrance to FSC. Instead of the courtyard in Jelly King perhaps a sort of labyrinth level or something.
This would definitely enhance replay-ability for your game.
bump