Greek as Greece nation tag or Greek nations overall?
If the first, i think the nation suppose something that comes very late in game, so i dont think there is a way to play it out with missions, except if you build something based on the revolution itself, new guirella type unique units, democratic or monarchical ideas based on specific paths etc.
If it is the second, the releasables are kinda irrelevant tbh and you wont really see them around in 99.9% of cirqumstances so i dont know if it is even worth it. As for Theodoro and Trebizond, which if i a not wrong they dont have a mission tree, they should definitely get one. Both are cool reminants of the ERE and could have unique missions or even alternate ones.