Is it unreasonable to assume the "White Snake" is something very like Fukasaku or whatever the Frog Teacher dude is?
Fukasaku is the Frog Sage, who has knowledge in the Sage arts, which is Senjutsu, using the force or energy around you.
In a way, Naruto combining with Fukusaku will grant him greater power, and whatever else. But in order to obtain this level, they need to ''Connect" to one another.
So perhaps the White Snake is the nemesis of the Frog Sage, in some way, since he has his own type of powers it seems. The powers of rebirth and eternal life. The power to steal bloodlines.
It seems Orochimaru has fused with the White Snake, in what seems like a permanant fuse. This has allowed him to continuously regrow limbs and body parts, because it's as Kabuto said, he's no longer human.
Maybe Orochimaru came the furthest in Fusing with an animal sort of like how Jiraiya and Naruto do with the frogs.
Anyway.... Your thoughts?