lately i've been chewing on the Sword & Planet subgenre. I've only recently heard of the name "Sword & Planet", I would have just called it Fantasy. Google it, you'll probably recognize more than a few titles and authors.
The main conventions are: Primitive Civilization. Alien Planet (or a twist, it's secretly future Earth. Planet of the Apes. )
And not always the case, the main character is a human from Earth - ideally from a time period close to modern day so you can relate and understand the character as they traverse an alien world and foreign culture.
So anyways, I'm been thinking about how to make a game within the genre conventions without transforming it. You have to take it past the medieval sword & sorcery that most rpgs currently use. Primitive, like animal skin loincloths. Maybe something like Monster Hunter where your equipment is made from bone and scales.
The hard part is conceptualizing the story. I'm trying to think "speculative fiction", I just haven't found a good "What if" to work off of that'll lend itself well as a game. I find myself making decisions and then realizing a lot of games went the same route. I hate to call it a formula when it's so natural and satisfying.
Start at the bottom as a slave, outsider, or whatever; End at the top as a Chief, Guardian, Hero & savior ect...
Raising in power is kinda what rpgs are all about, so many end with you pitted against a god.