All you needed to do was give a monk a simple item to enhance his unarmed strike like any other person can enhance their weapon at the regular costs, and the problem is "solved." Since the monk's entire body is a weapon and part of his singular "unarmed strike," I was always the most partial to making it a robe slot item.
I'll start. It's an extremely weak option for a monk along with basically every class, and even if it didn't cost two of your precious feats (it gives you free exalted feats back, but with only a few exceptions, exalted feats are garbage), I'd still not take it as a monk unless I expected the game to drastically deviate from the expected wealth by level (on the low end).
I've seen Vow of Poverty break a game. It can get pretty bad at higher levels.