I've been postponing hollowing out the wall components. Not because I don't want to hollow them out, but mainly because I got distracted by other things...
Very much inspired by
this little snippet I got intrigued by the idea of making separate bits that you could put on the existing model. So that you'd have the basic kit (walls and floors) but then can add all sorts of extra components on top of that. Rather than having to produce tons of different walls and such.
So first up, another wall panel variant:

It's supposed to be a safe, or a secret tunnel or something. I feel that it might need some more detailing though...

Pipes have always been a soft spot of mine, my first versions of these type of constructs included all sorts of advanced pipe systems running underneath the floors. This is sort of my tribute to those old versions. At the moment the pipe system consists of two components, allowing to connect to sides of the wall to one another. However, I might do some variants in case people make broader pathways and such.

Computer consoles are always a must in this sort of project. Here are two components, still very early WIP. The control console (the one on the bottom) still needs a whooooole lot of detailing and stuff added to it. The top one is almost ready, a few details here and there. However, both still need to be hollowed out to reduce material cost (both for printing and casting) and weight.
Of course there would have to be a wall panel variant with some larger screen and controls on it, but that'll be up next!