Alright, per definition can you not have a betting system without either p2p interaction or central authority. The question here is how far should CHA go, if the limit is p2p interaction then obviously you can't go far beyond dice games or roulette. The interesting part of the gambling world is in interaction with other players, though. So I'd say why not introduce interaction (at a later point probably, first things first)
There is already a coin/system that does that. And basically all people that invested in this coin don't want to trust somebody. The whole appeal of this coin is that noone can cheat here.
Lets look at it another way. Why is BTC so awesome? Nobody can manipulate the total number of coins. Same goes for CHA.
Now we introduce your sportsbet manager that sets the "fair" odds. What happens if he goes rouge or makes a big mistake? Like he creates 500000 new coins by accident (fat finger)?
This isn't all to unrealistic... Mistakes happen all the time.
I'd rather see a fork with those features, than see that implemented into CHA. CHA should focus on all the casino games that are out there. Slots, roulette, blackjack, dice, and many more...
A market is as fair as it gets, I'm not in favour of a sportsbet manager. I mean I think we're at a dead end here, I think you're excluding a lot of gambling by excluding interactions with other players (such as one of the most popular casino games, namely poker), but if you don't think so I can't change that and I see your point.