Three things:
1: Did you e-mail the fighters in question before you posted this?
At this time I don't want to judge whether your accusations are wrong and right (though I would certainly hate it if there was irregularities concerning a fight one of my characters had with one of the accused players characters), however, I think it's fair if the accused had a chance to respond to this before taking this to the public.
I don't know if, in fact, such correspondence has happened nor, if so, the response given, and I understand and truly appreciate that you wish to make sure that other fighters are aware of the irregularities.
Yet, I believe that even if they are guilty of the charges, people should be given a chance to redeem themselves, metaphorically speaking a yellow card or perhaps a two-minute penalty, before they are ostracized entirely.
Again, you're not the one on trial here, I appreciate what you did, but you asked how to deal with this, and the above is my humble opinion.
IF we are certain that irregularities have taken place in a fight it would be proper to regard such a fight as a forfeit by the irregular and a technical win by the regular player. If the irregularities aren't discovered immediately after the games, however, it poses serious chronological problems regarding the proper tier and rank of a character - and thus the validity of subsequent matches, and perhaps such technical wins should not have any influence on the rank and tier of the regular character, but instead only alter the wins vs losses ratio.
What to do about the irregular characters? Gosh, I think it's clear that such characters cannot remain in the game if their stats aren't proper. It would violate my sense of sportsmanship, that's for sure.
2: The problem of possible scams between two fighters. This could be a serious problem, for instance, if two players decided to pump up the ranking of the first player's character by letting it repeatedly pounce on the second player's character.
Now, Sash vs Sash is NOT inherently wrong (as you yourself point out) - it is minmaxing at it's fullest, but the rules were designed so that the Sash would wish to fight another Sash - just like Light vs Dark-fights benefit both in the long run.
3: Principles aside, I, personally, now consider Sollir on probation from this moment; I'll fight him, but not without judge-generated moves, and I won't accept him as judge. Sorry, Sollir, but those precautions stay until the air has been cleared. I'm sure you understand.