The highlighted is key. The Franks, and especially Charlemagne, gave harsh penalties to traditional practices wherever they ruled. The Scandinavian kings did likewise, reading the sagas of the two royal Olafrs, and civil wars in Sweden. Heathen practices had to be extirpated with fire and sword, because there was no popular opposition to them. England *might* have been more peaceful, but I don't know about Bede's reliability in this regard. Iceland's conversion was more or less peaceful in part because of how brutal Norwegian kings had been in bringing their people to Christianity. Even there, compromises were allowed in the early years, until the Church had been firmly embedded.
The recon part of me winces at this, but... it would be a plausible development and definitely increase the chances of a surviving and flourishing Germanic faith. Relatively minor change in worldview, probably still opposed by conservative elements (especially in places where Christianity isn't seen as a bigger threat, like Sweden) and adopted by kings to increase their power. As for a name, I'd suggest translating 'Old Tradition' or 'Our Custom' into Saxon. Written theology would be more difficult. I'd imagine more a collection of national and regional histories, origins of practices, lore, law, underpinning political and social traditions... but maybe I'm thinking too much into it. More a Tanakh-Talmud than a Gospel, if you get my drift. I'd caution against using either of the Eddas wholesale. Poetic has a few entries of questionable historicity (Rigsthula in particular) and Snorri tried to fit the Prose into a Med worldview, tracing the Aesir back to Troy to give his ancestors some classical dignity.
Uh, jeez, I tend to go on, don't I?