My idea isn’t bad, it’s provably best-possible. You’re welcome to math it out.
MMR is a normal. SR is a normal. SR is scaled on [0,5000]. MMR is scaled on [0,1].
MMR “maps onto” SR. Now, do you want that to be arrested at one of the edges (in this case, lower bound at zero), or do you want that pinned in the middle? The answer is middle everytime, because it avoids the most “collisions at the boundary” and offers a more efficient kinetic expansion of the players from starting location to final deserved destination. If they’re offered a free bounday + 1 pinned, then they get all these extra collisions at the pinned boundary and the MMR interactions are thrown way, way off. The “gas” (in this case large N players) doesn’t expand outwards from all sides covering the most region as quickly and with as little resistance as it should.
Middle is just better, because math says so.