In some ways this did happen. One of the reasons why Prussia didn't annex Austria for example was that the inclusion of a large catholic majority region was considered unpalatable to the Lutheran government of Prussia.
What I'm trying to do is pretty extreme though, I'm trying to get Hungary to go Lutheran, Bohemia to go BRETHREN (without that being ASB) and for Catholicism to be diminished in Austria to the degree that they are absorbed into Germany due to linguistic commonality and cultural similarity. I want the only Catholic nations in Europe to be Italy, France, Spain, Portugal, and possibly a few others. I want to see a European religious landscape with the fewest Catholic nations possible. Italy is a foregone conclusion: it is Catholic yesterday, today, and forever. I understand that were it not for the Jesuits that Poland would've become Protestant. Let's go so far as to make Ireland Protestant (not Anglican or Presbyterian, but definitely NOT Catholic dominant). The game is that I'm trying to essentially castrate the powerbase of the RCC only insofar as how they link Church with state in terms of authoritarian enforcement and instead have nation-states on the so-called fringes sponsor their own denomination/theology.
Also, what I would love to see is a valiant attempt on behalf of the RCC to enforce themselves on the rebellious/reforming nation-states, but failing miserably, thus resulting in whatever respective nation-state's theology becoming blended with nationalism, but not to a belligerent end.