"You may only gain points once from the same team in skirmishes per week."
Hypothetical situation- let's say Merry Men have a scrimmage against Corvus on Saturday. Both of us have point totals of 0. Say Corvus wins the fight, netting 1 point. Could we then decide to do another scrimmage with Corvus immediately after? Would it count for 2 points if Merry Men win the next fight (since Corvus would have 1 point to MM's 0)?
If that's the case, it could be exploited a bit to guarantee two colluding teams to get 1 or 2 points from each other each week. You may want to change the phrasing to "There is no limit to how many scrimmages per week you may play, but you may only fight each team once per week for points. You may, however, face those teams in a tournament the same week and get points."
EDIT: You may also want to put an anti-collusion clause somewhere in the official rules, and maybe a minimum size for a tournament (3 or 4 teams from 2 or more clans). There's currently nothing written that stops, say, The Ducks from creating a 2 or 3 team Duck-only 'tournament' multiple times per week (the Ducks are just conveniently large, not implying they would actually cheat the system). You could even say "Muse has final say on whether a tournament grants points or not. As long as it's not blatant cheating or against the spirit of competition, pretty much anything is fine."