So, what I'm thinking about doing, as a result of various discussion lately, is to use and expand upon Kobold Press' Beyond Damage Dice, add a few special attacks to the game, and treat based level martial arts proficiency as part of learning to fight.
So, unarmed strikes deal 1d4 for everyone but only people with martial weapons, and monks, get proficiency, Monks get the ability once per round, or again if they spend 1 ki, to use a special attack as part of an attack rather than in place of it, and the Kobold Press Beyond Damage Dice techniques become something you can learn much like how a wizard learns spell. Go find a manual that explains it, fight someone who uses it against you and then practice it, train with a master, etc.
I might use your feat as well, though if it still looks like it did the OP, I'd say that I'd add the following;
If you are already proficient with unarmed strikes, you can add your proficiency bonus to the damage roll of a melee weapon attack with your unarmed strike, once per turn.
This firmly makes such a feat good for a monk or a fighter with the unarmed fighting style.