If V2 is anything like EU3 and HoI3 (and I will assume it is since it is using the same engine), then all the relevant data files regarding provinces, nations and their internal contents will be text files and thus easily moddable with the use of notepad.
So I would wager yes, if you want to refine the cultural depiction of a province further, or change its total population, or add new cultures and religions, it most likely will be possible. Unlike V1 or the other games on the old engine, these kinds of labels/tags are not hardcoded or limited in number.
And that, alone, should make V2 a better game overall than V1.
the only limit i can see is that the more unique POPs you create in game, the more the game engine will have to do various daily calculations regarding their economic life, their political views, their MIL and CON levels, and the like. So, just as I've said about adding provinces in maps, or more new nations, it is mainly going to be a question of balance. Put too much new data into the game, and the game engine, combined with your processor speed, might decide to go on strike due to overworking. How much more data that would take to reach that point, though, is an open question since everyone's computer is going to be different.