So here's an idea, we have this amazing ladderweek leaderboard, why not use it for ladder division/season ranking?
Assuming you can get access to the system(pretty pls arkitect), just modify it to last the ladder map rotation/season timeframe(which can be debated) and use the old rules for giving out different points depending on what division(the limits for which can also be debated) your opponent is in. Sure, it's not perfect and there are issues with division allocation(smurf/previously unranked guy on top of division 4 atm, for example) but it's a hell of a lot more than what we currently have.
Not to mention it looks great(there's even a cool golden helmet for the leader instead of a boring number!)