Yes, I agree that it would be a nice part of the series as well. Kishi has given flashbacks for pratically everyone, Some being much longer than others like Nagato's story. I also think that the sage of the six paths will appear in Naruto's subconcious when he's about to die. Didn't he get a little piece of all the jinchuurikis when he pulled out all the chakra spikes during the bijuu battle that took place? Having all those pieces has to add up to something.
even better:flashback of madara and hashirama fighting.that would be epic!