I never really like the idea of using two stat bonuses calculating your entire AC in 5e. It's a holdover from earlier editions, when getting stat boosts through stacking bonuses from magic items, spells, and potions would allow for very high scaling.

There's a clear direction from all the rewritten subclasses, in that each one contains a method of either pushing away your target when you hit them in a variety of ways, or providing clear ways of disengaging from melee. Maybe this should just be placed in the base class, that 1/turn any Monk gets to push a target away that is struck with an unarmed attack, like the 'Shove' feature of the Tavern Brawler feat? Or maybe just giving Monk the 'shove' weapon mastery to all unarmed attacks, and the Monk gets to add other specific masteries as they level up?