I suppose it would require some hardcoded changes to add the title system.

The way I am picturing it, the general would get a tab on his unit card to be appointed the lord/marquis/baron/whatever, when he is in the region and the title is still up for grabs.

I think it would be funny also to have the titles that result from certain buildings, like "Constable" and so on, but I am not sure how the actual giving of the title would work in the game.