1.) There are going to be enchanted weapons in Skyrim. So I'm pretty sure that there will be enchanted bows/arrows.
2.) Yes . . . limits are what keeps things balanced.
It will be magical weapons, I also guess it will be magical arrows, however magical arrows was rare in Oblivion, I guess Skyrim is based more of reuse of arrows making them even rarer.
However I don't think this will be in even if the idea is interesting, it will not fit with the rest of the system as you cast a singe use enchantment on your weapon.
Another options had been if you could cast magic with left hand while the right hold the bow, makes sense as the hand is free. In game this depend on how bows are organized, if your right hand hold the bow and the left the arrows you could switch but you would probably not earn much on this.
Anyway a good idea for moders