This is just a few thoughts on this subject so be open to this and take a look at the big picture.
1. if it just so happens some type of way we are not in the Luck situation (even though i prefer LJ) Trade for Peyton M, resign Henne for 3 years and let Peyton Mentor Henne. Peyton will probably only play for another 2 years or so anyways. This does 2 things, allows WRs to see a real QB in action, also instantly bring back respectability to Miami and their fanbase. AT the same time Henne can be brought in as a cheap young backup that has the possibity to get better.
2. If the Luck situation does come about still resign Henne to a 3 year, cheap backup, and let him compete with Luck in the new system that whatever new coach will bring in. That way it will push both guys to get better. A-Luck probably reading about how bad Henne is will want to make sure he doesnt lose the starting position to him and B. Henne hearing about the suck for Luck campaign will try to show that he is a better QB than Luck and can lead this team. either way it would be a win win, if Luck beats Henne we still have a young backup QB for cheap and IF Henne beats out Luck then Luck will not be thrown to the wolves and can have some time to soak the NFL speed in before he gets a chance to be the starter.