Without giving away any of the developer diary coloured details, is the team's thinking on this influenced by Napoleon's conquests in Europe? The local AIs see an aggressive neighbour, so they get moody and try to stop the beast, perhaps?
Anything other than the traditional BB system is fine with me, honestly. In EU3, you could take Mecca in a holy war and gain the same amount of infamy for it with Christians as you do with Muslims! It was a really silly system because the concept of a single infamy stat implies that every country on earth views your actions the exact same way, which obviously shouldn't be the case.