Truly, there are no others? Is the Classical world so limp and colourless that no other would be interested, compared with the multitude of fantasies and sci-fi settings?
Scifi and fantasy are easier to write. You can make your own history, own race, own characters etc etc.
With historical nrp, people actually have to do research to play as a nation. You do not have the freedom of history, the freedom of race nor the freedom of character. (I mean, I doubt you'd have a ultra 'good guy' knight character in the persian empire during the greco-Persian conflict times.
Unless Ofcourse you are very loose with rules but then you lose the cultures of said nations.
With all that said, id be more so interested in the 4th option, as I know more about that time period than the others.. Though id still have to do research which is a
chore.