The stereo should still work, but you would still need to run the AUX connector to a new place on the fairing. Most of the face plate on the cassette box is used to hold the spring loaded door, and for the two inner fairing screws. You can probably do without the two screws, and if you can do without the door, you could cut a pretty large hole for accessories, like a glove box without a door. I think that it looks better with the door though, therefore, the slot would have to be pretty small.
J Richie