Two things:

Should this game be in 3d or in 2d? I would prefer 2d, I'm ancient. It would also be cool because the 2d platform game genre still has never been taken to the max.

I like the Marshmallow idea. We would have to drop the 'loosely related to Jazz Jackrabbit and in the same universe' idea, though. Maybe that would be a good thing. I'm kind of nostalgic, you know. JJ2 was fun, and I'm afraid that the next platform game wouldn't have the same feeling. But every game that isn't a real copy will have a quite different feeling, so maybe we should drop the relation to JJ2.

This brings me to something. It will probably end up failing, but why can't we ask Epic and Lost Boys Games if they would allow a platform game in the jj2 universe, possibly even with jj2 characters? If you don't try, you will never succeed. I mean, if even companies like Jaleco may make jj games, and terrible ones at that, why can't we? We would probably have to do away with the open source thingie though. Or at least, the characters would be copyrighted.