I am sure this would be a bitch to code randomize but why not halfway through the game create a reward challenge? Whatever team wins reward each player left gains a certain sum of Health/Water? Could help balance those who may not be on and are in need of such materials, and helps create an interesting situation that could flip what tribe wins.
What does everyone think? Feel free to discuss or even hate my idea. Just something I thought of and who knows, some changes may help me want to play more often again ;)
