I don't think the QB has to be elite either. Just a good one like Eli. We've been trying to build the O-line around here for years and years and years, so all we can do is keep trying. The amount of injuries inflicted upon that unit over the years is staggering, and even the one year where it was decent (2010), all of the receivers were bleh and we had a rookie QB. The stars just never seem to align for us.
I think Fisher's coaches *can* develop a QB if you look at it in a vacuum. We have good coaches in Cignetti, Wienke and Garcia, but they can only do so much when the O-line is dropping like flies and the QBs start to hear footsteps every time they drop back due to being pummeled half the time. You can teach to encyclopedic levels, but panic ruins everything a QB has learned in those moments. Which is why I'd like a QB who has already mastered fundamentals and a couple more veteran O-linemen as part of my off-season wish list. That, and a stud WR in the draft. While it would be nice to light up the scoreboard like a pinball machine again, I just don't think you can build two elite units and expect to keep them all signed. If you pair an elite defense with an offense that can average 24 points a game, then you've really got something. All things considered, I'd rather get into the postseason with that, than an offense that scores 37 and a defense that gives up 40.