Pointing directly to Juugo's Clan. I also recall that Fukaku said that Jiraiya was not the first man to become Toad Sage, maybe this first Toad Sage was from a different Path..?
You're good at linking different things together. The Six paths could refer to six different doctrines of combats or distinctly different traits. Doijutsu being the 1st, Life Force being the 2nd, Natural Energy/Sage mode being the 3rd. Perhaps Kabuto and Orochimaru also knew of these secrets and attempted to bring all of the Six paths into one body.
Notice how Kabuto took an Uzuamki's life force, Juugo's Sennin chakra, Suigetsu's hydrification and Kimmimaro's body.
Suigetsu could be linked to transformation, much like the Juubi is undergoing a metamorphosis into different states.
Kimmimaro's body has been brought up on several occasions and is thought to be the ultimate body, which in my opinion should classify as one of the Six paths.
I'll link you to a good theory if you wish
