Well, I feel that ELO ranking is more important in this case. There are many, many farmers who just quit when they are losing, and they are actually top players at some mods (or even they are in the top 10 global players). It's dishonest, and I think that they should lose ELO for it- anyway, I don't feel that their opponent should get any ELO due to it (it would allow farming too).

How about first leave each day= -0,75 ELO at mod rank and -0,5 at global rank + You are unable to join any game for 5minutes; every next leave: -1 ELO at mod and -0,75 at global + You are unable to play for +25minutes (second leave: 30minutes, next one- 55min etc). I don't know if it's possible to add it, but I think it could be good...
Oh, and TC tournaments should have their own rules, like leave from a tournament= You are unable to play toribash for 2hours + unable to join any tournament for 48hours or so.