I was thinking we could get 16 contestants, and then we do 4 rounds (with 4 fighters in each obviously). The best 2 (if drawn the one with the most KO's progresses (if still drawn do a 1v1 match)) from each match will progress giving us 8 left. We repeat said process again, but with only 2 fights with 4 in each, and the winning 4 go into the finals. The winner of the last match wins.
I don't really want to restrict things to 16 people just yet, it's better to see how many people are going to be interested before deciding if 16 is good. Either way, we should give everyone freedom on what time they have for the matches, restricting the whole tournament to just be during a few hours on one single day will restrict how many people are available for it. If the idea is to do a tournament weekly, then giving people the whole week to finish the tournament should be fine. Obviously it will be easier to see how things work out as time goes on, but if a tournament is going to be weekly, then we may as well let people have the week in case they get busy and can't do it all at once rather than forcing them to forfeit.