First off, how do you know he'll be third string? You don't.
Second off, Brady is 36 and injuries are a part of football.
Third off, there's a thing called the wildcat that's en vogue. Teams like to use it at times. If the Patriots do at all, then that'll mean a chance for Tebow to be an impact player.
Fourth off, I've never seen Tebow as anything but a QB sink or swim. In theory, he could play full back, but I don't know why he would really.
Ryan Mallett is firmly entrenched as the #2 quarterback...he knows the system and he's got a cannon for an arm. My belief is that Tebow will be converted to tight end. Belichick loves to run two tight end sets and he loves players that give the other team match-up problems. If Tebow can catch the ball (and I have no idea if that is the case) then he's got the speed to elude line backers and he's too big to cover with a safety. There aren't a lot of coaches that could get Tebow to try a new position...Bill Belichick might just be that guy.
Do you really think that pro tight end positions are that simple that you can just pop anyone in there and they can pick up all the technique to be successful in one year?
Tebow is going to be a QB, and I think it more likely that Mallet is going to be traded at the end of the season after getting a lot of playing time to show him off this year. I think he is OK with that and likely tired of waiting for Bradey to retire. Tebow I think is willing to play back up till 2016 or so while he learns behind Brady and improves his game.
Never said that changing a player's position was simple, Jim but probably the players most able to make a transition such as that are quarterbacks who basically have to know what the all the other players on offense are doing and are generally some of the more intelligent players on the team. Belichick has a history of liking cerebral players that CAN play different positions. Let's face it...there was little interest shown in Tebow as a quarterback in this league. The Patriots signed him for the veteran's minimum so they have not invested a large sum of money in him if he doesn't work out. He is a smart guy, he's an athelete and he's willing to work his butt off. If he wants to play football in the NFL he's either going to have to demonstrate that he can throw the ball better or he's going to have to play another position. That's reality.
Mallett is definitely trade bait because he HAS learned the Patriot's system and he's got elite quarterback skills which makes him a valuable commodity either backing up Tom Brady or by becoming a starter on another team via a trade. Belichick doesn't make that trade however unless he likes whoever would step up to be Brady's back-up and Tebow isn't even close to being that guy at this point.