How possible would it have been for the Scandinavian kingdoms to take up Orthodox Christianity? The idea was inspired by Crusader Kings 2, to be sure, but disregarding the game, I think there are some compelling reasons why it would have been possible. There was, after all, some possibility of cultural exchange due to Norsemen travelling to Byzantium to join the Varangians, as well as eventually the adoption of Orthodox Christianity by the Kievan Rus'. Could the Norse have converted to Orthodoxy, and what changes would be required for this? What would be the consequences?
(Denmark, Sweden and Norway all seem to have converted to Catholicism between the late 900s and early 1000s, as far as I can tell. The Rus' took up Orthodoxy in the 980s. Was there any attempt to introduce the Orthodox variant of Christianity to Scandinavia before the 980s? Or would we have to delay the Christianization of these kingdoms to stand a chance of introducing Orthodoxy? Denmark probably has every reason to go Catholic due to its proximity to the Holy Roman Empire, but Sweden and Norway, perhaps, have a better chance of going Orthodox? I wonder how that'd change their foreign policy... I imagine the Swedes would seek to push into Finland earlier to link up with their Orthodox brethren in Russia, and would perhaps also be on friendlier terms with Novgorod or its equivalent later on? And the Catholic-Orthodox divide could potentially be a lot more violent if there is another front for this conflict at Scania...)