Pep wins a close decision. Pep is a bad style match up for Chava, looking at the Cowell and Ford bouts, and Pep is a higher class. Sanchez would adapt aggressively later on, but it would be little too late at that point. This match would be one for the purists. I would pick Sanchez to beat Saddler, though.
My thoughts on this are almost a carbon copy of yours. If Sanchez had a weakness it was against cagey guys who could keep it long. He was good enough to still beat decent (and, I suspect, even the very good) fighters of this kind, but Pep is a whole other proposition. Think Pep outscores Sanchez more often than not. But like you, I back Sanchez against Saddler, big time. I think Sal walks him on to just about every counter jab and left hook he throws. Great as Saddler was, he wasn't an adapter and I think by the end Sanchez would have him looking a little clueless and desperate, much like Flanagan did. Pep had problems with Saddler's sheer physicality and will, but I don't think he'd be able to impose it on Sanchez. Sal could handle himself when things got rough and a bit dirty. Three greatest 126 pounders ever in my eyes and I see them as a nice 'styles make fights' triangle (although I accept that 3-1 against Pep might flatter Saddler a little). Pep too cagey and elusive for Sanchez, Sanchez too sharp a counter puncher and too rounded for Saddler, Saddler a little too marauding, powerful and dirty for Pep.
Styles. Really bad matchup for Sal.. This is no walk in park for Pep either. I recall Pep was sitting at ringside for the Sanchez-Nelson fight and was quoted saying something along the lines of "I'm glad I didn't have to face him." I think Pep was being kind. Not an easy night's work for him or anybody else, but if he comes in prepared he outboxes and eludes Sanchez enough to win a fairly close decision.