Yes and no.  In theory the controller can become the engine, so to speak, inside a myriad of shells, but in practice it won't happen.  Developers have little interest in deliberately shrinking their potential market.  A few variations will emerge, a fishing reel, a gun, a steering wheel maybe, but that's about it.  Probably 99% of revolution software will only be compatible with the remote thingy and the included analog stick attachment.
So, IMO, you shouldn't give it too many points on expandability because, while I agree that developers CAN make it whatever control they need it to be, I do not believe that they will.  I think that for the most part you should judge it based on its potential out-of-the-box, since that's what the vast majority of developers will program around.  Fortunately, that potential is still enormous even without the expandability.