@Albertese - Thanks
@Bob - No worries. As I've indicated before, this is just one possible version of the Enterprise. We all have our own personal canon on how she is suppose to be
As to the "back wall", we're never shown what that would look like and the filming model also lacked a back wall. I thought of a back wall or perhaps a large door there but alas, the TCOTK observation deck changed things a bit so that is where this version is.
I would like to point out that the "Brandon" approach from "Galaxy Quest" is pretty close to the "Thermian" approach since they did include the "chompers" in their plans and the sequence of operation. The "Thermians" however went one step further since they had to fill in the technology and all the equipment not shown on-screen based on what they were told that it could do. I obviously lack the technology to do that, but I don't mind trying to fill in the out-of-camera-view areas