Hmm. We can monkey with how this all works inside of initiative too. One issue, 5e has is no delay action option, and ready isn't the same thing. Perhaps that would be a good thing to add to the class at level one? It would let him float around in the intiative order a bit and make better use of synergies. That's an aside though, in the case above, perhaps if you spend the Ki to grant advantage and the attack hits you get your attack back, or you spend two Ki to grant the advantage and get one Ki back if it hits? Call it Tactical Feedback or something.