Oh, very cool idea. It would probably only work for actual WP8 apps at first (not WP7.x apps, as those would require either a Silverlight or XNA runtime), but the idea has merit for sure. It was speculated for a long time that running WP8 apps on Win8/Windows RT would be possible, as both are written against the WinRT API, but that never happened. If we can make it happen ourselves, though... that would be awesome.
Of course, ideally we'd want to be able to access the store, since there aren't a lot of WP8 app packages floating around where we could use them. That's probably a very tricky problem in and of itself, although you could try extracting the store EXE and seeing what is required to make it work...
Win8/Windows RT Projects:
List of desktop apps for hacked RT devices
XapHandler, Root Webserver, OEM Marketplace XAPs, Bookmarklets collection (Find On Page), Interop-unlock hacks.