Maybe I'm mistaken because I haven't played it as much as some people but this is pretty similar to Mount & Blade. I think if the NPC factions simply did more and were more effective at sieging one another it would be that almost exactly.

Similarly, Dwarf Fortress Adventure mode is almost exactly this but it leans deeply into roguelike survival and is still part of the old school ASCII version.

The problem is if you're just a pawn in a dynamic procedural strategy game against NPCs it seems very easy for the factions to be procedurally put in a situation where one AI absolutely dominates another and the lack of control you would have over the bigger events would become frustrating.