You've ruined this board for years, and for whatever reason, you are allowed to do it, but now you're being serious?
I'll humor you:
Harvin would help to restore talent at the WR position that he had back in 2010, his best year, his second season.1) Sanchez's ability to read a defense.
2) Improve his decision making skills.
3) Eliminate all his INT's and fumbles.
4) And most importantly, improve his accuracy?
The argument about Sanchez' ability to read defenses is overblown, the turnovers aren't always the result of an inability to read defenses, as was the case last year, it was everything to do with Sanchez not being on the same page as his receivers, this entire topic was well described in the "pass happy" thread.
IMO, the shift in offensive philosophy of the WCO can help Sanchez as much as anything, in addition to removing the 'ground and pound' mantra that Ryan has tried to instill in the team.
A philosophy shift, the hiring of a competent QB coach in Lee, will do more to improve Sanchez more than a player can, but obviously Harvin can certainly help in several areas
Harvin is a player defenses have to respect, he can stretch the defense, create separation, make plays, help to restore Sanchez confidence, this alone will improve the trust he lacked last year with his entire offensive arsenal, last year, he had a musical set of chairs at WR it seemed each week, one week, wit Marty Gilyard picked up off the street, Clyde Gates, and Chaz Schilens as his primary targets, all due to injury.
A legit supporting cast, an offensive philosophy that doesn't smother the passing attack, and quality QB coaching will help Sanchez the most, along with maturity. His inconsistencies, deficiencies of accuracy, and turnovers are a product of all of these factors.
How is it that Harvin doesn't help?
How is that the Lee hire can't help?
It's obvious Sanchez struggled at the end of the year last year due to confidence issues, that more than anything will deter a player, make him gun shy, influence his decision making, impair his ability to execute and read defenses, if Sanchez can put last year to bed, and go back to restoring the fundamentals of the position, and trust the philosophical change Mornhinweg will undoubtedly bring to the team, and for the first time, not have Rex and his iron fist on the "ground and pound," I think this will all help the factors you elude.