What would be cool would be to add a challenge setting that allows you to accept rematches, regardless of rating or game limits. The time-constraint limits would still be restricted as the person challenging for the rematch can change those.
Sometimes I, or my opponent, want to initiate a rematch, but can't due to a limit. As a result, messages need to be exchanged to work around it. If I could just set a flag to allow rematches regardless of my settings, that would be GREAT!
So, in practice, when you hit the rematch button, it would also pass the game-id of the game. That way your code could check to make sure that it is a rematch and not a hack.
Another consideration would be to limit the time period to 2 weeks. If after 2 weeks a rematch has not been issued, then any rematch challenge would be treated the same as any challenge and must meet the rating and max-games criteria of the challengee.