Some intangibles to think about, would Peyton want to go to an NFC team and in doing so hinder his little brother's chances of getting to a 3rd superbowl, or would be rather stay in the AFC and face him in one. Just a little snippet from my pocket of irish drunk knowledge. Although many see Washington as one of the favourites I dont see Peyton wanting to play against his brother twice a year. Maybe I'm wrong though and time will tell.
If he comes here though I will seriously feint and as much as I love Tebow the player, he'll never be half the QB Peyton Manning is/was.