It is a Skill Level Match making, it's called Skill Points. If they ever go back to GP Matchmaking, although I'd do pretty well...I'm quitting. The games moved on too much to allow it.
What it does need is an Activity Score:
Each player is given an activity score, that doesn't affect rewards in any way. The max Activity Score is +10 and the minimum is -10. Players are matched on Skill Points (as they are now). However, instead of playing the nearest 7 players to them, there is a secondary matching system which is the Activity Score. Players play players with the same Activity Score, rather than the nearest 7 on the table.
If you score 0-10 points in a GAC with 0-1 attempts you score -2 AS points.
If you battle more than once, but not more than teams deployed in 1 zone ( or 2 battles in total for leagues with only 1 team defence zones) you score -1 AS points.
If you battle up to the amount of teams for 2 zones (3 battles for 1 defence zone leagues) you score 0 AS points.
If you battle up to the amount of teams deployed for 3 zones (4 battles for 1 defence zone leagues) you score 1 AS point.
If you battle as many times as there are defensive teams (or 5+ battles for 1 defence zone leagues) you score 2 AS points.
As stated earlier +10 and -10 are the max/min scores, so once you hit these numbers you hit a ceiling/floor until you start to lose/gain AS points.
I think this is a very simple and elegant way of fixing GAC. It prevents big rosters that fall from playing against those that do play.