There is currently no way to do by tech group or region or country. I understand the same ships are used by all subject to reaching the necessary tech level. I posted a request to allow more flexibility but it may be igorned.
The proposed changes would just add new ships for everyone once they hit the required tech levels in the naval.txt mod.
The changes mainly add more flavor by having a lot more ship types over time. I tried to maintain balance by having historical ships by era. For example a big impact is in 1530 when the galleon era starts. I also had more powerful galleys, transports, and light ships also show up at the same time to maintain balance - but only if it made sense historically. In other words I built the new ship types first - then tried to line them up within historical reason.
At this point I have built the changes for standard NA 2.2 and consist of the new units, one new localization file, some new amins, and a modified naval.txt file. In other words the work is all done for NA 2.2. All I would need to do for you is to see what is non standard about your naval.txt file.
If you want to include the work for your mod then I can upload the finished work to you by the end of the day.
If you are not interested then let me know and I will post in the forum a version for standard NA 2.2 and if requested versions for other mods - just as an add on option like you do for your map (old map or regular).
Of course it goes with out saying that it is your mod and you can change what ever you want. All I request is that you give credit to me and to the two inactive mods whoose work I started with - namely Dougs Naval Mod and the Combo mod. Also mention that Merlins ship graphics are included.
Best Wishes
