That doesn't sound very interesting at all, I'd recommend that you stay away from original Cave Story maps, music, characters, and storyline as much as possible; these things usually make for more boring mod.
Not that I play many mods anymore, but this was main problem with CS Mods: they just followed up on the original story. I played one and it was neat (Lost Land, Carrotlord's, iirc), and now I'm done. Most people don't really enjoy CS spinoff #9000000 unless there's something new and interesting about it, and this honestly seems boring.
If you want to make a difficult platforming mod, just make your own without CS, it doesn't even need a story to grab people's attention. Just leave Cave Story behind, for your own sake.
Also, it should be noted that this is thread #3333. Lucky you.