User blog comment:Pacificus Viridis/Gaul Rising/@comment-32656-20120330073102/@comment-4940710-20120330161732

Why wouldn't the Germanic tribes agree? Postumus is offering to let them take a bite out of Rome, which they had been wanting to do for a long time; and the Germanic tribes would have a realistic chance of getting what they were promised, considering the situation Aurelian is in. Aurelian still has troops trying to retake Gaul and Spain, he has to deal with a brutal invasion of Italy, and he'll probably have to deal with assassination attempts and usurpers as a result of Rome being sacked for the first time in 662 years.

As for the alliance with the Germanic tribes costing Postumus support, well, that is possible. On the other hand, I think that after fifteen years of internal stability, the people would not only be willing to forgive him to some degree, but by this time begin seeing themselves as citizens of a new Rome. This alliance would keep the Alammani from causing trouble in the Gallic provinces for at least a while, and it could be justified under an enemy-of-my-enemy mindset. Besides, there are plenty of examples of longtime enemies reconciling in OTL, so I'd say it's within the realm of possibilities in this timeline.