When Nagato said Jiraiya could win if he knew the secret, it simply meant Jiraiya would fight a wheelchair Nagato, nothing more and as mentioned above, the statement is merely a hyperbole and it isn't meant to be taken literally. I have no idea how anyone else interpreted that statement other ways, when Jiraiya barely won against 3 Paths thanks to element of surprise, which caught Nagato off guard as he never thought Jiraiya could cast Genjutsu on him. Every Ninjutsu Jiraiya threw got absorbed and Taijutsu was useless in front of shared vision coordination. He never stood a chance and he said it.
Even with all those backups, 6 Paths of Pain still win medium difficulty at the very most. It can honestly be a one-shot, if Chibaku Tensei was cast off the bat, but that would be out of character.
-Mu is irrelevant because everything he could throw gets absorbed by Preta Path. Bansho Ten'n and Ningendo combo ends him.
-Gengetsu gets dealt with quickly. If he uses Genjutsu, Rain Tiger detects the clam then the Genjutsu is cancelled by either summons, rockets or ST destroying the clam. If he uses Joki Boi, it gets pinned down by black rods incapacitating its movements permanently. Gengetsu is then killed by soul absorption.
-Rasa doesn't have any defensive structures as Gaara does to protect him from offensive techniques Pain can throw. Chakra Canon Propulsion or Shinra Tensei or Rinnegan summons shits on his Gold Sand, then he gets his soul taken out.
-3rd Raikage would get handled in the same manner Kisame handled Killer Bee. Preta Path simply grips him and absorbs his Chakra, then it's a matter of time his soul is ripped off.
Jiraiya got stomped before and it happens again. Orochimaru himself gets killed is self-explanatory. Either Chibaku Tensei or large scale Shinra Tensei is also a one-shot, so Deva Path on its own can comfortably solo this.
