You'd end up with bare aluminium and unless your putting a protective clear coat on it it'll need redoing a lot as the oils and crap from your hands will mess it up!
Personally I will be surprised if this ends up happening this time. With the 4 and 4s it was so simple to remove the back and really difficult to do the front but this time it's the opposite.
I dont know how your phone has scratched so easily.
I'm literally grinding mine off a wooden desk as I type this, and its causing no damage at all to the phone. My desk meanwhile, will be falling apart if I continue for too long.