I can't stand the jets or their coach. Don't really care for Tebow, either-- but make no mistake, this is a good move all around.
Why it works for the Jets--
O.C. Tony Soprano will take offense from anywhere. Remember the wildcat? He will surely make a package for Tebow to highlight his skills. giving up picks for a backup is questionable, but Tebow will play every game.
In addition to his value as a niche specialist, they have someone to motivate their other qb to be more of a leader. Sanchez has teammates calling him Lazy. Here he gets a push from a guy with certain leadership skills that can even step in and finish a game for him if he looks like he's going to blow another game. Sanchez insurance/ role model.
If I was the Jacksonville owner, this is a huge disappointment, but the coach? with such a fanatical fan base, the coach would not be able to bench the guy. In New York, people are mostly not expecting a gridiron messiah like they would in Jax.