Except you won't. Please tell me, how do you know you're getting a 5th for him in compensatory pick? Are you aware of how compensatory picks are given? Playing time + Salary. Matt Moore, coming to Miami for 2 years 8 million dollars, and starting SEVEN games (which he'd be lucky to start if signed by a new team, let's be realistic) was only worth a SIXTH ROUND PICK to the Carolina Panthers, who signed next to NOBODY in 2011, the year Moore was lost.
Okay lets say all your variables come true and Miami is on their way to getting a 5th round pick. Are you positive Miami isn't signing a big name WR? Or even a middle tier WR? Because that'd cancel out losing Moore. You don't get a comp pick if you sign a free agent equal to or better (more playing time/higher salary) than your loss.
Third, MY fifth is worth more than YOUR fifth. It'd be worth a SIXTH (in 2013) because it'd be in 2014, not 2013. Except, it wouldn't have the same value, because you are unable to trade it, which I expect they'd do (why else would you have so many picks that will likely not make the team rather than trade up and grab someone you really love?)
Your scenario has way too many variables. I'll take a 5th for Matt Moore. The season would be lost if Tannehill went down anyway, so why plug the leak at the expense of the future? Seems foolish.
So no, you won't get a 5th round pick for Matt Moore in the compensatory system. You absolutely trade him for a 5th round pick from the Arizona Cardinals if they call on Week 8 and make that offer. You have to answer me those 3 questions before you can begin to say a single word with any type of confidence regarding compensation picks for letting Matt Moore walk