Here's my current thinking.
4 judges with a variety of tastes and preferences.
Each round is 1v1 match ups in a league format. If there's not a huge number of players we just do a single league (I guess maybe maximum 10, which would be 9 rounds). If there's more, we do groups and then playoffs.
Each judge has 3 "goals" to award per match, and can award them either 2-1 or 3-0 to the song (s)he prefers depending on the strength of that preference. So each judge has to choose a preference, but a match can still result in a draw because there are an even number of judges.
Haven't decided how league points will work yet, open to suggestions. We could go with a football/soccer approach in terms of 3-1-0 points for win-draw-loss, and use "goal difference" if necessary to decide between tied players.
Basically what this means is that in each round, a player just needs to beat their opponent, but because the judges will have different tastes, it often won't be clear how to do this, so there should be a fun element of tactics and strategy.
EDIT: And there'll be no need for lengthy write-ups, just a sentence or two from each judge explaining their scoring.
EDIT 2: Oh and for banned list, the four judges would agree on a list of the more obvious ones but it wouldn't be very restrictive. The focus would be more on fun and figuring out how to beat your opponent, rather than music discovery for the judges (though there'll probably be some of that still).