Well, if you do that conversion on the EGG-INFO directory of an .egg file, then you'll have a wheel. At least, if I understand your spec correctly. (Since .egg contains just the code and static files.) All you need to do is get the egg's platform info and Python version from its filename; everything else is in .egg-info. The full spec is here:
http://peak.telecommunity.com/DevCenter/EggFormats But basically, it's just going to be just convert EGG-INFO to Projectname.dist-info. The actual layout of the rest of the zipfile is essentially unchanged.
(Heck, add .whl support to pkg_resources, and wheels will have all the advantages of eggs as well. Though, for that to work under 3.x some of the stub file stuff would have to be changed as well.)