This would be a very niche thing but I don't see anything wrong with it. As long as it's just betting between friends then we really don't have to worry about manipulation of the final outcome. It would be like betting on pro wrestling. You know that the result is predetermined but only a few people know this result ahead of time.
No matter who is the winner, if we are betting between friends, we might not feel too regret because we know one of us can be the winner.
That will depend on how good we play on that game and if we can play together with our friend in one place, that will be a pleasure to us.
Even if the manipulations can happen at the end of the result, sometimes we do not care because we only want to play the game with our friends.
But it is better if the result will not get manipulations to be more attractive to see the result and the winner.
Sounds right, as long as you have a friend/set of friends who are willing to place bets here, sure. Just as usual, mostly your cousins would be the ones who would be willing to do it with you.
I still remember the days when I and my cousins would place bets (real cash) on our school mates kid fights, we were in primary school. Associating it with your post, I guess the principle is the same. As long as two parties are willing to place bets, there will be no problem with it.