Hi! There is a suggestion similar to this before, click here
Although the betting system you are suggesting is quite good, and would be amazing, it may be hard for the GM to monitor everything (since there are may be a lot of players betting and it would be hard for a GM to facilitate that). If this would become an automated event, it would cause some bugs to the NPC that will facilitate the betting system you are suggesting, and it may even irritate you. (Eating your tokens for example, not sufficient tokens given, and even giving more than what you should be receiving which could ruin the economy sort of issues)
Another issue for the GM is this, there are 15 players who bet this "fighter" as you call 'em, and about 5 of them DCed and never came back, when shall they get the tokens back? What if they received the tokens already and claimed that the GM kept it for himself? And what if the player never returned, and the GM is stuck with the tokens? That is why we don't ask or be traded for anything, it is not allowed to keep items from players, because it would lead to issues such as this. We are stuck with "what ifs" and that is not good.
And..
The forums part would take some time, which would make the participants leave since it is taking too long. And trust me, players don't want to wait that long. As simple as having to wait for a GM to invite you to a party is already irritating to some, that's why we are looking for an easier and faster way so you guys won't have to wait that long. Although being patient is the solution to this, not all can do that.
The best solution I could probably suggest is this, make it an automated event or even just an arena that anyone can go to (You won't be able to receive anything from it, it's just a game) and input a time limit. Let's say there are 3 games there, you could choose Game 1, which has 5 min time limit, Game 2, which has a 10 min time limit, and Game 3, which has a 30 min time limit. The suggestion is actually doable, but having the betting system just complicates things. The Gladiator style Event is feasible, we can produce a 1v1 match, and probably an audience area just to watch the match, but betting on the fighters, or maybe we can call them "gladiators" is a No No for me.