I think the main problem is inactive/disinterested players falling lower than they are intended to be. The current system is great if every player does their best every time.
I think the lower leagues should be protected from these players to keep it fun for newer entrants to the system.
Here's my solution: create a gp floor for each league. If you are over a certain gp, you can't fall out of that league, once you have climbed into it.
A problem with this would be that players moving up could meet an ocean of these inactive accounts that may be impossible to beat, or horrible to come through. Further solution: players above the gp floor limit can still get a lower and lower skill rating, down to a lower limit well below the entry skill rating for the division. So you end up with a pile of big low activity accounts with a skill rating about, let's say, 300 below the points where a player that just climbed into the league starts. The player will immediately only be encountering active accounts, with maybe the odd person diving into the obscurity pool. The main thing is that these plunging accounts don't ruin the fun in the lower leagues.
Players who decide to become active again will take almost a full GAC month to climb back to the competitive area, if they want to. Players that just get 10 points per fight, or don't sign up at all, hang out in the obscurity pool, away from everyone trying to enjoy the game mode.
I don't think I'd have a kyber obscurity pool, but probably having one for brozium, chromium and aurodium would help with this problem.