I have encountered this ragequitting problem a few times again this week and it's the biggest gripe I have with players' tactics. I have encountered a few players (particularly boii but also unforunately Sc00rp) who quit just before a loss simply to maintain their rank, so this problem extends further than just tourneys.
My suggestions are that should a player ping/disconnect/quit etc during a fight(doesn't matter why they leave the fight):
-The losing player has their elo rating reduced, maybe even more so than it would have been had he/she just lost.
-The winning player can be assigned an 'inconclusive' and their elo would remain unaffected (to discourage people from using multiple accounts to rank someone up, should that be a concern - otherwise the player who stuck around can be awarded a win. I think this would be better to trial run and if people do use this to rank themselves up the person who stuck around would just have an unaffected elo rating).
-The match itself can be categorized inconclusive. The reasoning behind this would be that, if there weren't enough legitimate matches finished during a tourney no prize money would be paid out (as it currently is) to prevent farming as has been mentioned, however, if there were enough matches during the tourney that did finish and the last match is inconclusive due to someone ragequitting, the winner can still receive the prize money that he/she rightfully deserved.
If possible, the above suggestions can be wavered should a disconnection occur BEFORE the first frame (though honestly if you want to stick around to chat just /sp).
I believe these types of implementations are already enforced during duels (though I'm not certain) and if this is the case I'm guessing (hoping) implementing them wouldn't be too hard and would help combat this problem.
Last but not least: If someone does ping during a tourney, they should not be able to rejoin the tourney. People seem to have caught on to the fact that if they are losing, they can ping and rejoin the tourney and have another shot at the prize.
I'm sure there are people who would be put off by these ideas, but I do unfortunately have days when I ping a lot (mostly not during matches, but at times it would be in a match and people would refer to me as a ragequitter which I hate) and suffering these penalties, even if pinging is beyond my control, would be worth it if it can help stop people taking advantage of the current system and causing a lot of frustration for the majority of the players.
The idea of an ingame rep is also very appealing, since people tend to behave themselves more when someone with authority is around. How the screening process would work I'm uncertain of, but if such an idea is to be implemented I would happily volunteer as this type of behavior is unacceptable to me