What System For...?

[MintRabbit]

A game where the events being played out are themselves in question and of a mythic nature (meaning, in practical terms, that continuity and certainty are themselves uncertain).

Hmm, in that case I think I misunderstood your original question, so I don't think the games I had in mind give you what you're looking for.

 

[Wofano Wotanto]

A game where the events being played out are themselves in question and of a mythic nature (meaning, in practical terms, that continuity and certainty are themselves uncertain).

I've never actually seen it or even a deep review so it may be completely useless to you(being based on D&D 4e strongly suggests that), but there's a Santiago RPG based on the Mike Resnick novel of the same name and the broader setting/future history most of his scifi lives in. A major theme of his stories and the Santiago books in particular is the way myths accrete around real people even in the distant future, so maybe the game has a focus on that aspect of things.

Spoiler: Book spoilers

Santiago, for ex, has a "Dread Pirate Roberts" thing going where it's more a title and rallying point for resistance to a distant core civilization that's slowly moving into the frontier zones - it has obvious parallels to the American West and many of the characters are effectively living tall tales, most of whom fall short of their legends in the end.

If you can find a good deep dive review or someone here can provide one maybe it's worth a look. The game engine doesn't seem ideal for what you're after, but maybe I'm wrong and there's something as innovative as Lancer or King of Dungeons hiding in Santiago.