i'm agree with ibrahim about battle list, player can choose opponent but if strong player choose weak player with skill below 20-20-20 will get no point, get point while meet player with skill above 20-20-20 to 30-30-30, then above 30-30-30 to 40-40-40, or above 20-20-20 to 40-40-40 ..... continue to max skill.
there is no max skill
and better to tell in % skill difference, not in numbers.Now you can join 60% weaker opponents battles, i think it's fair enough.. i will see how big the gap will be, but i cannot do nothing with other players activity