rate player

I think it will be a great incentive to play fair.
After a game, you could rate your opponent as to how fairplay he was.

This rating would be shown next to the elo of the player.

What do you think?

(I am sick of people that don't play for the remaining of the time when they loose)

The principle is nice, but the idiots, rude people and cheats could abuse your system. So you might be perfectly nice and one of those people could rate you badly. Also, by the time you check on a person, they will have lost interest and looked for another game.