So as a hard working, rank grinding individual, I run in to this problem a lot. I'll be waiting 3 - 15 minutes for a match, then right before I win, my opponent leaves. Sure, they get punished, but I just wasted a lot of time, and for no gain. Give us elo based on our current elo and the elo of the opponent that left, therefore it can't be abused. Please consider this.

-snip-

couldnt this be abused for farming elo or something

there should be something regarding frames played to elo gain imo. It would discourage abuse. If someone left at the last moment, you could still be compensated.

I think thats something that should be considered if anything here.

Maybe add a score variable to the elo. If you're ahead the opponents in points and he leaves, it makes it your win. Might not solve everything, especially in dq-based mods, but it'll be a help along the way.

As someone who often plays tk I can relate. it sometimes happens like 5 times in a row.
My suggestion is: as soon as someone gets points, the elo rating will increase as soon as the opponent leaves.
This would prevent unfair elo change in the following situation: Tori is afk. Uke waits 2 turns, realises the afk and leaves.

Yeah. I agree that both the elo should be based on the elo of player who stayed and the player who left as well as basing it on frames so that if they leave on the final few frames of the game it awards elo rather than from the start. If you play enough ranked games either in tourneys, matchmaking or ranked servers you'll have experienced quit games and spectating and it is pretty frustrating.