Have you considered the use of the OpenSCAD library NopSCADlib?
The library https://github.com/nophead/NopSCADlib offers a number of advantages:
- Contains a variety of non-printable parts ("vitamins") including bolts, stepper motors, pcbs (including RPI4 and stepper motor drivers). This includes dimensions and helper functions for these parts, so standoff and bolt holes could be automatically given the correct positions.
- Having the vitamins makes design easier, since the fit of parts can be checked while working on them.
- The library contains involute gears, so the current gears could be replaced with a version that does not give a warning in OpenSCAD.
- The library does contain a build system, but that does not need to be used
I'm not suggesting wholesale conversion to the library, rather just using the library where it is advantageous.
I've just quickly wrapped the existing stls with some NopSCADlib vitamins to show what can be done. Note the bolts, pcbs (including RPI camera) and stepper motors.
And here's the exploded version.