Actually, here is a good example of this, conceptually.
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A large boxing ring is 24 ft by 24 ft. That means from the red corner to the blue corner is 34 ft. This means, mechanically, the absolute worst situation for a monk to be in... is in a martial arts ring. They are at their worst, when they don't have the room to get away from their opponent.
This is part of why I want the d10. Monks should not be scared to be in melee. I'm also give them the swashbuckler's ability at level 1, so they can disengage from people they've attacked, but this I think speaks to something in the class. Maybe Monks need more AC, or a way to utilize their mobility defensively, but as designed they struggle at the one iconic thing a martial artist is known for... getting into a ring and having a 1 on 1 bout.