Ship of the line is actually simply going to be a different looking Frigate, for England, Spain and maybe France, to reflect their superior navies. It's not actually going to have different stats.
Sorry Sword_Of_Geddon but I'm going to stick with the "looks only" approach to this mod. Getting into different stats and trying to balance them and what not is just, well for one it's not as fun, and plus it's tons more of work which I just don't have time for. However, if you or anyone else want to take all those "new" units and make them actually new and unique then I have no problem with that. At the minimum it's just a change to the units file, and if you wanna change their names and pedia text it's only 3 more xml files.
It will however remain as a patch/add-on to the mod and will not be included in the mod itself because I still believe there's a "market" for mods that don't change the gameplay.
As for diversifying the cities, yes and no. There are several considerations here. First of all, I don't want to reuse the warlords city sets because I just feel it'll be giving too much of Warlords art for free to people that didn't buy it. This means, that it'll have to be made, which brings me to the second point. I just don't have the time to create new city sets. The reason I included some of that stuff is because it was already done for me (I took it from another mod), all I needed to do were the XMLs. I will limit myself to only diversifying the Palaces (because I'd like to work on more structure modeling in general) but even that is going at a slow pace because of time constraints.
Having said that, if someone creates more city sets or palaces then I will include them, if they agree and as long as all I have to do is modify the XMLs.
Cheers