Aaaand done! Well, sort of. I’ve now completed the game as every single nation at least once, and in every possible way at least three times. So it’s complete.
In terms of outstanding achievements, I have a few “do X on Deity difficulty” ones which simply are not going to happen, and the “win before 1000AD on King” which is plainly impossible. There’s also a “don’t change governments, and win on King” which should be possible, so I might give that a go.