Quote Originally Posted by Theodoxus View Post
The why is simple. The desire is to keep casters from easily grabbing the martial benny once again with zero impact onto their functionality.

If Focus doesn't play well with Concentration, that's a good thing. How you make that happen is of lesser import than that it exists.
The why from the OP is actually to fill unused design space.

I think if your goal is to give martials toys that casters can't abuse, you're far better served by binding those features to things like the Attack action, weapon attacks, Strength, and class features. Concentration slots will still get abused by casters who want to hold a buff without the risk of losing it. Darth Credence's first post contains several effects that a caster would be happy to snap up.