Well, I can't help you with that.
About "2" it is not an issue for us in Europe. Superheavy cruiser or any other fancy name will not change the fact that those ships are battlecruisers and you can already build them in game. (Alaska, B-65) *I am not aware about that dutch design.
In theory, for anyone interested in editing the files, it is possible to increase the gun limit for the cruisers in the "ship types" and then limit the gun limit for all cruisers hulls launched before 1930 by editing each hull individually in the "parts". I am not sure now about the armor, but I think it is possible to reach similar result using the same method.
"1" and "3" are interesting ideas, but I am already exhausted. I am at moment living abroad with little time to do anything. My plans is to update for the new 1.6, import the new hulls and guns when they become available, then add new historical destroyers I hulls for some nations and I am done. After that, anyone is free to do whatever they want.