In Europe, it would be viewed by most people as the merger of two dwindling institutions, both of which are losing membership every year in every major European country in which they are present.
The evangelical churches and movements, which are growing in Europe, would view this combined church as more a real estate deal, with a united owner gaining control over a lot of valuable property. As far as a movement of followers of Jesus, I cannot imagine that the would want anything to do with this new Orthodox/Roman Catholic church. Why take on the problems of these dwindling institutions when their communities are vibrant and growing?