How about a different class feature for the monk?
Immediately after you are hit with an attack and the attacker is in reach, you may spend one ki point make an unarmed attacks as a reaction. If you spend two ki points, you may make the attack before the attacker hits you with an attack as a reaction. If the attacker is still able to make the attacks after these attack, the attack occurs as normal. Any effects, powers, feats, or abilities that require or use Flurry of Blows allow apply to this ability instead unless specifically stated different. This ability is taken instead of Flurry of Blows.