An idea to counter disabling new champions in ranked
Require a champion to be used in pvp (any form) for a minimum of x games, i'd even recommend 20 games.
Not "own 16 champions" or whatever it is, but make it so new champions, and "first timers" cannot destroy "ranked" games which by default should be competitive as is. Also helps prevent elo-boosting and the like as the buildup to ranked becomes quite hefty for the new "mains".
It would definitely need improvement... but something like this could prevent the crap that happens