There's a game that already did that, Sword of the Stars 2.

Widely panned at release due to being forced to release old code after VCS failure, though I'd argue the only problem after patches were left was that movement logic change didn't play out well (it was a brave attempt though).

Had some bad performance issues but I never tracked down whether they were related to SQLite or issues in their engine.

Well, of course there is. Here I thought I'm doing something somewhat original...

Fortunately, existence of prior art doesn't invalidate any of the goals I had for this experiment, so I'll just carry on with it.

Of course it does not invalidate your experiment, but I wanted to suggest maybe looking at save files from the game.

Are you referring to the rougelike Sword Of the Stars:Pit or to the base game itself

No, I'm referring to 4X Sword of the Stars 2 itself. The Pit happened later, on a different engine (SotS2 is heavily windows-specific .NET code with DX10 dependency, iirc)

That's super cool. I think that approach is quite scalable, too. Only games with very complex logic would require something faster than SQLite for game logic.

Unrelated, but I also guess that using SQLite for offline data could be a timesaver, since you can leverage web tech to make tooling for your artists and level designers.