I will try to think the solutions to do a Power Leveling without touching much the elo.
So here is the mains sources of problems:
1) players with multiples accounts/friends play against themselves/friends, and win/lose in purpose and drains elo like that
2) games with high number of players will lead to having way more match-up than those with 2 players
3) playing 10 times against the same player and doing 5-5 should not lead to any extra loss of elo
4) players at the top of a leaderboard on non/few luck games got absurd winrate which can in non luck game easily be 95%+ (having an expected winrate of 90% against a new player and doing 9-1 against them should not lead to any extra loss of elo,
i think?, or maybe a middle ground need to be found)
5) playing arena with random opponent should not lead to extra loss of elo
6) less popular games got fewer players to play with
I think all of that is a mess. Even just lowering k-factor which is the obvious solution would be 'why doing that?', why gain and lose less elo when you play a lot against someone?
Checking all those things server wise seem really bad (per example by keeping history of loss/gain of two players), you want something simple to check X times per game.
Checking this only for players >400 elo would not work since if you play 200 times against the same player, that lower player would not get the penality even if he loses in purpose.
So, if you start a list of previous opponents with duplicates, and take the last 100 ones, then look for duplicates in thoses, then do the sum of the elo gained and loss against each of those players (removing the k-factor in those), and look for too much gain (or loss), maybe something above 30 elo (3x a single victory at 50/50 odds) you could apply that formula.
This look lots of work though for every game.
And it doesn't resolve points 5) & 6).
