Is your feature request related to a problem? Please describe.
It is a feature request, and I think it would be nice if the cabs can be made so people can have a choice on what the elevator should look like based on their preferences.

Describe the solution you'd like
I would think that there should also be elevator cabs that don't have glass walls and doors that don't have a glass pane in the middle along with those that already have them.

For the cabs, you can just implement the feature as part of the Lift/Elevator Refresher tool. As for the exterior doors, my personal viewpoint suggests that it should be controlled with the Brush tool. Currently, the brush is set to only control whether the doors is locked, so it should be changed so a pop up a menu would show up, similar to how its used when customizing the floors. For example, it can look like this:

[_] Locked
[v] Show Glass
Door type: [ Center-Opening ]

The door type, in my opinion should include single speed left, single speed right, 2 speed left, 2 speed right, and maybe 2 speed center opening, and if you want to get a little crazy, have them go up or down when opening or closing.

Additional Information
Other suggestions I would recommend, but aren't as important in my opinion would be to add floor passing beeps and the option to configure the chimes. (Such as changing the pitch and sequence to mimic that of real elevators). If it is too much for the base MTR mod, there should be addon packs that people can download if they feel like it.

I second this. This would be good because the elevator design that is currently available is very generic.