Other way around. The text http://en.uesp.net/wiki/Lore:Reflections_on_Cult_Worship puts the Imperial Cult of Tiber Septim as a "Nordic hero cult". Which makes sense, given that Ysmir is a semi-divine figure among the Nords and Talos being seen as Ysmir is part of the reason they joined him to begin with. Talos' official story even capitilizes on Nordic cultural themes, like being blessed by the Greybeards, coming from Atmora and such.
Anyway, Wulfharth would side against the Empire, because he wouldn't bow to elves. Tiber Septim as he was in life would probably side with the Empire. And Zurin Arctus is an unknown.
As for Talos the God, I leave you with the words of Wulf:
- Ghostgate: "This is a helluva place. Why are you here?"
- Perhaps I should keep my business here secret: "Suit yourself. I don't know why you'd bother to keep anything a secret here. I was just wondering if you might be headed inside the Ghostfence to Dagoth Ur."
- I am the Nerevarine, and I go to confront Dagoth Ur in his citadel: "What a piece of luck! Look. I'm an old Legion veteran, as old as the poor old Emperor, bless his soul. I'm too old for campaigning. I came this far to look at hell. But I can't go any farther than this. I'd take it kindly if you'd carry this old lucky coin with you when you go to Dagoth Ur. Sort of a token of the tough young hero I used to be. Would you do that for an old man?"
- I'm sorry, but my mother told me never to accept gifts from strangers: "You're a suspicious sort. But maybe I can't blame you. Worried about a request from a strange old man in a strange place like this. Well, I won't press you. But I would sure be grateful for the favor, if you could see your way to changing your mind."
- I'll take your old lucky coin to Dagoth Ur with me: "That's very kind of you. Here's the coin. I've had it with me a long time, and it's always brought me luck. But I have no more use for it, and I'd like to pass it on to somebody younger. Somebody going places I can't go anymore. Your generation's shaper of history... an engine of destiny. That coin will bring you luck on the mountain. I promise. 'For Emperor and Empire,' as we say in the legions. Go with Kynareth."
- Poor Old Emperor: "The Emperor is getting old. Don't know how much longer he'll hang on. So is the whole Empire, for that matter. Getting old, that is. The Emperor and the legions have held the Empire together for hundreds of years. It's been a good thing, by and large. But maybe it's time for a change. Time for something young and new. What? No idea. Because I'm old. Old dog doesn't get new ideas. But maybe young folks like you should try some new ideas. I don't know. Could be messy. But change is never pretty."
- Wulf: "Wulf. That's me."
Edit:
While I would like to see more of the Nordic pantheon in Skyrim, things doesn't seem to be that simple, and I generally applaud the game for it. People and traditions change over time, and we see that in Skyrim. The Imperial version of the divines, which itself was a merging of Nordic and Aldmeri ones that later lost some of their Aldmeri parts, are very strong in parts of western Skyrim, especially Falkreath(Arkay), Solitude and Whiterun(Kynareth).
In Riften, however, we have the Nordic version of Mara and Kyne referred to, and Talos is as much a Nordic god as an Imperial one. "Ysmir, Dragon of the North" is a Nordic title and he is worshipped as "Protector of Man" and "Patron of Nords". Clearly more leaning towards his Wulfharth side. The Temple of Dibella in Markarth seem to be neither Imperial nor Nordic, but a version unique to the Reach. You also hear numerous references to Kyne and Shor by Nord NPCs.
Certain gods, like Jhunal and Stuhn, are mostly gone, but those have been known to be mostly gone among the Nords since Morrowind. Other gods, like Arkay, has no inate counterpart among the Nords, and being adopted by them makes sense. A god that opposes necromancy would have had to come after the fall of the Dragon Cult, given their extensive use of it.
in short, I think a lot of the changes to the divines, while I would have liked to learn more about the specifics of the doctrines and such, is a decently presented case of how gods change and merge with outside influences. Despite having carried on many traditions, Skyrim now is not the Skyrim of the 2nd Era, which itself was not the Skyrim of the 1st Era. Which in turn was different from the Atmoran religion of the Merethic Era.
Edit 2: Also, who is talking about "the old ways" among the Stormcloaks? I got curious, so I looked up Ulfric and Galmar's dialogue, but they talk most about being free to worhip their gods. Ulfric mentions following the traditions of their people, but that doesn't need to be religious. I know there is a reference to Ulfric challenging Torygg in "the old way". Which is perhaps a bit of a misnormer for the duel, since Sybille Stentor explains the legal rammifications, meaning that it is still part of the local law in modern day Skyrim. Just not commonly practiced.