I had some free time and kept playing around with the previous fast, dirty, ugly, and simple object to see what came out and what other options could be available for walls.
I'll stop with this one here. I know it's not the GDL Forum or the Object Depository, but I still wanted to post it here since it is still related to floor-to-floor height, and the code is somewhat commented and could be useful to other people.
It´s a simple cube, with automatic height adjustment, with height options of manual, to next story, to top story, top bounding box and a specific story. These could be added to walls as well, of course with further study.
In its current state can be used as a 3D vertical shaft opening, that you can put in the bottom story, set its height to the top one, SEO from other slabs and forget about it. It'll self adjust to level changes.
If/when I develop it further (pens, materials, backgrounds, etc), I'll post it to the Depository.
Cheers everyone!!!