I actually read recently that at some point (probably a long time ago) they said they've thought about it, and they don't want that to happen (to have him use a weapon when his animations are unarmed), so they're thinking about something like, if you use a staff, then it has sweep capability, and if you use fist weapons, they support faster, less-damaging attacks. So you have a choice of fighting style that's dependent on your weapon. I think they said you can't use certain skills that don't go with your style of choice. I thought it'd be interesting to see what they come up with, but I guess they didn't go somewhere with that idea after all (or maybe they will yet).
Personally, I think it could've been way cooler if they made the monk more close to real life, by having him not need weapons to fight, and thus be the only class that doesn't need weapons (maybe even armor, or make the monk's armor always be enchanted cloth of some kind, even the best ones, but I think that having an armor on you, even for a monk, is much more in keeping with the spirit of the diablo universe, so giving the monk some metal pieces in his armor is ok all in all). You'd gain damage increases through your skills somehow.
Edited by Greenburger on 27/09/2011 01:59 BST