I think 29 is too old for a QB to develop into a franchise guy...and Weeden shows no signs of becoming one. McCoy was way too overrated coming out of Texas. I'm sure the thoughts of him being good in the right place are echoes of was thought concerning more than one of the QBs trying to succeed Jim Kelly.
Even so, Kaepernick, Wilson, Marino, Brady, Montana, Young, and Warner have all shown you don't need to be a top 15 pick to lead your team to the playoffs.