Mutual one-on-one games

This idea is stuck in my mind, I'd like to run a game with it:
- post-apocalyptic desert setting
- low-magic world
- weird arcane sandship, which is the only way to find other islands of rock out of line-of-sight, without getting lost in the arcane storm of the deep desert
- you can discover a world which was once a verdant planet
- if you want to, you can find out what happened to it, and find a way to revert it back to the beauty it was once
- discover lots of smaller, local power groups and make them allies or enemies

And I would want to play a game as well, something fantasy. Two ideas:
- a low-rank thieves' guild member accidentally acquires supernatural abilities, so she becomes a big player, influencing the city, and trying to save it from some sinister threat
- a veteran mercenary finds an artifact, makes a pact with it, does jobs for it in return, and also uses its powers for his own

I can do D&D 5e old version (with spheres), 5e 2024, AiME or Pathfinder without spheres, but I'd prefer Savage Worlds, Fate, or the nWoD core book, or Heroes of Adventure.

Well, it's interesting, but are you only open to fantasy?

Not only fantasy. I hoped I would find someone for that, though.

What do you have in mind?

As a player, I'd like some modern + occult, or sci-fi + occult, like Delta Green, New World of Darkness, The Void, Aliens, etc.

As a GM, though, I'm fine with fantasy, and the second idea really vibes with me.

Would you GM using Heroes of Adventure? It's free and very easy to learn.

I've never heard about The Void before, but it looks interesting, and PWYW is very attractive. I'll have a look at it -- inside it, actually.

Wow, a Delta Green player, I don't see those everywhere.

I always seem to find myself in chronic one-on-one situations lately, which is why I was reluctant to check this out, and I'm already in a semi-desert/Dark Sun-esque type setting, so I don't really want to be in another campaign where I have to be in some Dark Sun type campaign even if it's not with Elves. I could probably take a crack at running either scenario you present to be GMed, though, going through my interpretation of it might not be your interpretation, and I also then have the one-on-one case of just letting a character just running wild which is somewhat tough to do given the systemic limitations you list outside of homebrew, so, I don't know...the scenarios as a player scream Macguffin Munchkin to me for the second one, while the first one is a Tripwire Threat from some kind of threshold where they just "accidentally" Munchkin then it's just a one-person grindfest with goons with theme park dressing.

I'm not here to say it's bad, some time at the carnival is worthwhile, but it's pretty straightforward what's happening with a set up like that.

So, every sorcerer, every warlock, every caster, every martial artist character is a 'Macguffin Munchkin' because they want cool powers and to actually use them.
You have a very bleak imagination if you can't see any other story in a person who gets supernatural powers then "becomes a big player, influencing the city, and trying to save it from some sinister threat"

No, I have a very active imagination, and so I imagine you would like to succeed. I've run several one on ones. Pretty successful ones with plenty of vibrant worlds and scenarios. One-on-ones run very different than a group campaign, and I already said it wasn't something bad necessarily, but they have to be carefully executed. If the player doesn't succeed, they become miserable campaigns and the dynamic between GM and Player gets awkward, quick. So, the trajectory, naturally has to be success...well that means, in the parlance you're getting the thing, the powerful thing and going for a ride, hence my synopsis, but whatever, enjoy your game. I wanted to see what your tolerance was for other ideas for GMing something outside of the desert idea and the systems you use, and conversely your ideas what your tolerance was for seeing some bending around with those ideas, too and whether you were completely set on system, too. Nevermind.