Not much different than if Bradford suddenly had a top 5 year.
Stafford pre-2011
18th in USA Today power rankings behind Sanchez, Flacco, Freeman, Bradford, Cassel
19th by some dude at Bleacher Report
19th by John Clayton ESPN
So he was "pretty universally one of the bottom 16 QBs of the league." Yeah, he still had upside. But so does Bradford, I guess. At least members of the SF defense think so.
Did people question Brees' talent his last couple years at SD? No. No one thought he'd turn into Dan Marino but he was a good QB.
There are backups you should own/acquire for cheap, and Mallet is one of those. Not that I think he's hot chocolate but he will start for another team probably next year, and he will be dramatically overvalued when that does happen in the same way Ivory will be once the NYJ trade goes down.
Saying "let's get all these backups" or "lots of backups become great QBs" is bad advice. Cousins' only value is a handcuff. Osweiler not much more than that. At some point the roster spot is worth more than most of these backups. Their upside is no more than what Palmer is now, to be honest, and you have to blow a spot on them for 2+ years in order to figure that out. It seems to me you're not really evaluating the players, and just saying they have to be better than the garbage we already know is garbage. Really I have more faith in Carson Palmer putting up VBD in any season in the future (which probably means 2013) than most of those guys. Volek value is still value.
Alex Smith is not without upside too. Why did Foles have value last year? Because Reid made him hurl it up to 50 times per game. Why does Foles not have much value now? Because Chip Kelly will never ever NEVER have him hurl it anywhere near that godforsaken amount, and Reid wasn't able or wiling to trade for him. Unless the NYJ make another trade, Foles may never get another chance to start, and it certainly won't be as advantageous as 2012.
Would I roster Palmer or Smith over Mallet? No, of course not. The writing's on the wall there. Over EJ Manuel. No, his upside is a little more substantial. But yes over Osweiler, Cousins and Foles. In shallow leagues none of these guys should be rostered - not the garbage starter, and not the 2+ years away backup. In deep leagues depth is depth and garbage stats still count whether for you or the other team.
If we're picking backups, I'd even make a case for Chase Daniel over Osweiler, Cousins and Foles. But I'd still rather have Palmer now, and pay a fifth for Daniel later.
Really my strategy has been to turn your advice on its head. People will overvalue the mediocre prospect who hasn't failed yet. If you can get a garbage QB and a pick for Foles or Osweiler or Cousins, that is a great trade, because the pick is the most valuable part. There will be more garbage backup QBs coming soon for you to pin your hopes on and hopefully sell before they fall face forward or get cut waiting in line. Will Zac Dyssert and Landry Jones even be drafted in most leagues?
I mean, I agree we should learn something from Kaepernick. He was undervalued last year. He was dropped in two of my leagues for chrissakes. But rostering Kirk Cousins hoping he starts in 2015/2016 isn't what I got out of it.