That was an excellent discussion (and I cannot stand Zac and Elwood normally) going into the history of cars that tried the midgate concept. Sadly its a history of unpopular cars and inefficient solutions, but it does point out how useful a solution it could be for the cT.
With the dual backup cameras to feed the two screens being able to change the bed into just another part of the interior under the tonneau cover would make for a great secure storage or camping solution. Elon already said that the bed would be part of the AC system, what better way to accomplish this than roll down the rear window or put down the whole midgate.
And I love the idea of the midgate keeping what is dirty from what is clean. You can powerwash the bed after hauling gravel and then put down the midgate and load up on 4x8 panels and close the tailgate to securely lock them in.