I'm been avoiding this thread because i didn't want to vote on it. Initially I thought some of the detail that followed an option sort of tainted the option in a manner I didn't like. But I just can't shut up.
I guess I feel that because every campaign is indepenant I sort of feel that the answer to this question is novel at best.
So I play in a game where the 2nd/3rd edition inclusion of Tremere dabbleing in vampirism resulted in the Renounciation and destruction of House Tremere. So what?
I love the Ars5 version of the Tremere and I don't expect anyone to follow the nuanced covenant-centric history of my game. My specific game has dramatically changed the nature of the Order of Hermes. It has also changed the nature of the Church. In a world where the Church 'for sure' knows that magic is real, in a real world history where the Church at least discussed what to do with heretical off shoots, Inquisition and Crusade were not the only answers. Our campaign had a tenative 'get to know you better' truce between the Church and Order. No one save the top-dogs seems to like this, but the upper echelon is pushing it forward as the massess of both wizards and priests protest.
This is my campaign, I wouldn't expect anyone but the troupe I'm part of to play in it. So I'm just not sure about this topic. I suppose if the publishers of Ars are reading this then I would adamantly say, No fundamental change.
I say that because the core setting is so inspiring it allows you to have the options above. It allows you to make a Order at odds or at peace with the Church. It allows you to have a militant Order or a democratic Order or a completely disorganized weak Order of Hermes. The core setting allows for each of us to explore Mythic Europe in exactly the way we want to explore it and not make us right or wrong.
I guess writing this post and has made up my mind. For me personally, the answer would be a change in world, Order, and History. In terms of how I'll vote, "No Fundamental Change."