I leveled a new Monk up to 12 with the free XP available, not much gear available there, so I just had my Korthos wraps. Messing around in the GH slayer area, hoping to pull some wraps, and I started getting "you don't meet requirements ..." for stunning fist. Not surprisingly, my wraps took too much damage and fell apart. It seems weird that I could not still use stunning fist with unarmed attacks at that point. Also, for core bread-and-butter type weapons like Quarterstaffs, it would be reasonable for stunning fist to be usable in that context as well.