Putting aside the curved walls vs. flat walls discussion for a minute, just how big would this diorama end up being if built around the 7" Art Asylum TOS figures? Bigger than I thought!
Using the McMaster bridge blueprints and screen captures as a guide, I came up with the following:
The cutting mat is 12" x 12" and the wall behind Kirk is 8.5" tall. The doorway is 4" wide. (The camera angle makes the door opening appear taller than it is in relationship to Kirk. The actual gap between the top of his head and the top of the door is about .75".) The alcove is around 10.5" wide at its widest point.
The width of the alcove is wide enough that the doors could be made to slide out to either side and still be hidden behind the alcove walls.
The interior diameter of the turbolift car is 8.25" at its widest point.
How much of the interior of the car could you see through the door? More than I expected.
And here's a screencap for reference. When I recreated this with the 7" figure everything looked in proportion.