Russian cultured countries also have one.The one final big concern for me is NIs that actually give unique mechanics to specific nations. For example:
Inter Caetera: Allows claiming of colonies
How exactly do you balance this with other nations, when as of yet, I haven't seen any other NIs that do anything other then just give numerical bonuses to specific things.
Siberian Frontier: +1 colonist, and auto-exploration of all territory adjacent to owned home territory.
And "allow claiming of colonies" is a very vague statement. We know next to nothing about what this means in terms of mechanics since there hasn't been a colonization DD yet. It could mean that Castile/Spain gets the 'claim colony' action that was in EU3, or it could mean something else entirely. It would be best to wait and see what it actually is before passing judgement on it.