There's been quite a lot of comment in other threads here from people who would like to be able to produce acceptable notation by playing a midi device into a scoring program. The problem of cleaning up an existing .mid is a little different thing, but would also be useful for the same purpose - just a separate "cleanup" program.
There seems to be a recognized problem. The marketing guys will be quick to tell you that doesn't necessarily mean there's a ready demand for your solution, although the potential interest might make it worth looking at the possibilites.
A "dirty .mid in - clean score out" kind of thing sounds like a good deal.