Hey.. Im a bit of a newb to the xbox scene, but will try to offer up my idea.
with the release of caustik's exe-> xbe program, the xbox community is getting closer and closer to developing new programs legally, especially considering that the open sdk is well on the way. My emulator idea is of the port of the open source playstation emulator known as pcsx. I am an avid dc - scener, which is where i got the idea for this. Marc Grilenkov already made a port of this emulator to the dc, but unfortunately my all-powerful dreamcast just chokes through such a program. Since the xbox is a much more powerful machine (and i believe that a port to the xbox would be MUCH easier), why not some handy programmers give this a tackle when the tools become available (unless they use xdk. . .) ..
heres the link to the homepage of the pcsx project. . http://www.pcsx.net/
just my 2 cents