Well since you bring it up, there were a couple of games that released something like 8-10 years ago that would fit the bill. Both were open world FPS-RPG hybrids made in Ukraine I believe.
The first one, which I actually played, was called Precursors. This was a science fiction game where you could travel to different planets (as in, actually fly a spacecraft from one planet to the other) and land on them. Each one had a different and unique setting. There was a large scale war going on and you were a soldier basically doing quests for different people in different places.
It looked kind of cool as well (forgive the screenshot quality from 2011)
The Rock, Paper Shotgun review said https://www.rockpapershotgun.com/2011/01/04/wot-i-think-precursors/
This is the trailer to show you what the game looked like - https://www.youtube.com/watch?v=wPUSVg2wYXM
The game was broken as fuck. As in, game breaking bugs that stopped me from finishing it, but I have to say that it was overflowing with ambition at the expense of everything else.
The other game was called Xenus 2 - White Gold. I never played this but my understanding is that it was a game similar to the first Far Cry. You're on an island causing havoc for the local ruler or militia over there.
Here's a small preview article from RPS and another trailer that shows the game in action - https://www.youtube.com/watch?v=wLFTrR0YEko
Both games never reviewed well and in fact didn't get much coverage at all. They're not available on Steam but they are on Gamersgate. It's one of those things where the idea of playing them is far more interesting than actually playing them, but they were fairly unique games nonetheless.
i actually had a lot of fun with precursors
really goofy intro that was recorded by the cd making company (also yea the framerate was AMAZING) aside, the game was pretty entertaining, like u say lots of ambition and wonky gameplay. like layers upon layersd of unpolished gameplay, it was crazy
xenus i never played cos it has a giant spider in it -__-
the two games were also released in the west on the same fucking day which is kind of hilarious
i also enjoyed a lot the prequel to xenus, boiling point, which is even older and kind of plays like a budget deus ex/nolf game mixed with some farcry? that game also had some hilarious voiceacting and the most ridiculous bugs ever like second floors on houses no having any collision and flying cougars and shit