I didn't catch it when it was first announced, and don't read all the comments on WDA after the first day usually.
But an elf can become an arcane archer without any Rgr class lvls, and like you mentioned sneak attack weapons work for anyone. There is definatley precedence.
The enhancement line would be best for rogues, but could help any halfling who swings a wep (or even ranges)....esp if he adjusts his way of fighting.
And would it stack with weps of backstabbing? (prob yes)
My Halfing Thowing ftr might be even better. (at close range anyway)(and from behind)