I've not read the replies yet, so I may be repeating something, but yes, it would be very bad. Nintendo gets ideas for some games, and can build a system around those ideas. If they were a 3rd-party company, they'be forced to develop games into a normal box, which would really remove much of the Nintendo charm. I also think that's why Nintendo has said they'll never be a 3rd-party company- they don't want to be defined by someone else's box.
-dunno001
-On a quest for the truly perfect game; I don't think it exists...