Those are all great ideas roryb, and the Great Dragon Hunt's a fantastic hack I'd love to do something with. (And it's all there ready to go!) If you want to go with that I think we can add a few little touches to it and have a great time.
The zoomed out ages-long story could really work for PbP, and there's a lot of ways to get imaginations whirring with the looming death of your once-mighty race, so I like 'The Great Dragon Hunt' as-is. We could add some Dragon Clan element to the backstory to explain why our party is all working together, and maybe give the Dragon-Clan some remaining loyalist human servants or servant-races like Dragonborn or Kobolds to pad out the politics. I'd also like an extended backstory of aspects for our long-lived creatures as a way to record our centuries of wars with different races, kindness shown to other dragons, or any great marks on the land left by our deeds that might effect the legends we build up in the eyes of mortal races.
The Norse angle doesn't add anything to it to my tastes though. One of the things that greatly appeals to me with a Viking concept is the vicarious sensation of man against primal nature. Sailing your longship through rolling stormy sea, trudging on through the cold biting frost, wrestling your axe into the Troll's neck. A world where men sail in dirgibles or where Dragonbreath is a WMD takes away that exact kind of individual struggle and flight would take away the sea flavor. It's why I was going for LOTR as the parallel, Magic is a big deal as a guide and an enabler but everything still comes down to individual strength of will. I could see Norse style serpants, big swimming snakes with poisonbreath, being a cool addition taking on a kind of symbiotic role as chinese-style sources of wisdom and lore but contemporary dragons take away what I find cool about Vikings.
I say run with 'The Great Dragon Hunt' but while I found the Viking-concept cool, and I'd like to do something in that direction eventually, I'm not enthusiastic about trying to mix it into a Dragons game. (I don't object either though if someone else wants to do it, I just wouldn't take it too seriously.)