I know that Audiosurf 2 has a similar mode (i think it's called jump?) you basically just jump over and duck under obstacles to the beat of your selected song. I'd still love to have this implemented into osu! though, as Audiosurf never really got the rhythms PERFECT.
RdManebog, it's a nice suggestion, but there's no need for a character selection. Like in CtB, you'd be able to change the skin and make your own character/use one that already exists! (Hatsune Miku? >w<)
Interesting idea for a new mode, and while I think the game is fine with the current modes I will admit It'd be nice to see something new like this. I'll give it a shot. Support.