I have one twist regarding tribe separation. Rural vs Urban. It's the only unused 'stereotype' I can think of where it's people like farmers or from the country against modern civilians or city slickers.
Twists I've experienced in online Survivor games.
1. Everyone has an idol (not totally feasible unless there is some control/limit over ot)
2. There is this sort of immunity item. It is given to a person who doesn't have one in each round until one person left doesn't have it and is eliminated. Some notes:
a. it can be obtained by finding one somewhere, being rewarded it after winning a challenge when deemed by tribe as MVP, etc..
b. if a person who has one is eliminated before the twist finishes, that person will have to give it to someone else who doesn't have one yet.
I am more interested in culture-related twists though. That's why Amazon, Pearl Islands, & China received so much positive attention. They took advantage of the super strong cultures of the Amazonians, Pirates & Chinese.