After watching the latest episodes, I just realized... Don't read beyond this point if you haven't read beyond this point in the manga or only follow the anime. It's never told what the importance of Pain using Jiraiya's old foes was, other than to illustrate that Pain's bodies were fake. I mean... He would have to use the path that Re-animates/ generates the bodies, cause... seriously, Jiraiya was shown having defeated that first body Pain used to fight him, just slightly after he first met Nagato so that body would have been long decayed. So why did Nagato go through the trouble of finding his master's former foes and re-animating/ generating them? Keep in mind he didn't become twisted until a few years after Jiraiya left them.

Like a twisted version of Jiraiya's journeys? I mean, it could fit in a twisted way, the whole surpassing the elder part...except in Nagato's part he killed and used his old master's foes' bodies as weapons.

They were just strong opponents that Jiraiya fought and Nagato knew about.

Yeah, but why chose them then when he could've had any bodies, and they would've all had the same abilities anyways?

He was Jiraiya's student. He must have described his stories to him and possible have Konan find them. I suppose it must have been to make Jiraiya's life a little harder; there were bound to face each other sometime.