Getting old with the GP disparity - every level is having this problem besides Kyber 1

I could imagine that recalculation of skill ratings would take into account GP difference and GL-mismatch. If you lose vs. more GLs and/or more GP, then you don't loose much skill value. But if you lose against an enemy with less GLs and/or less GP, you drop further in skill rating.
And of course if you can win against more GLs and/or more GP, you gain more skill Value than against a weaker enemy.