Yeah, sorry I didn't announce this properly yet, let's do it right here right now then! I'll transfer this thread to the new Features section.
For who hasn't read my
latest blog post about it, I created a new workbench, called BIM, that is in the addons repository (install it with the Addon Manager).
There is still lots of stuff that doesn't work in the BIM WB. And there will be for a long time. If you find something that doesn't work, it's normal

It is made to experiment. It is not meant (yet) to be a productive environment. It is meant to experiment, discover and build what would be a ideal "BIM workflow".
The idea behind it is to separate the pure "technical" tools (ie. the Arch tools) in one side, and be able to concentrate/experiment with BIM workflow on another side. That's why I created this WB, so my experiments with UI don't pollute the Arch and therefore the whole FreeCAD source.
Also, with a smaller and separate WB, this makes it much easier for people to look at the code and help.
The main idea of the BIM WB is to use all the necessary other tools from other workbenches (so far Draft, Arch, some Part tools, and I'll integrate the flamingo tools better later on), add a couple of useful macros here and there, and that's it. If some of these tools need to be modified or new tools added, that will be done in their original WB and not in BIM.
The main focus of the BIM WB would be to create a new "layer" of interface on top of all this: Wizards, setup screens, dialogs, etc. The idea is to explore what an interesting BIM workflow would be, how it could be more intuitive and easier to learn.
A first thing I began to play with is linearity: When you open the BIM WB for the first time, a welcome dialog pops up, telling you what to do next. Then the next step suggests you a third step, etc...
Another thing I started playing with is "manager" dialogs. Manage all the floors of your project in one place. Same for windows. And more to come, with @paullee's suggestions above. Indeed there could be one to manage all the axes. All the site settings, all the materials, etc, etc...
About the floor object, it never really worked the way I wanted. After 0.18, I'm thinking to 1) rename it to something else, the word floor is confusing, maybe levels? But I would like something more generic, that is not necessarily stacked on top of each other and 2) make it based on App::Part, which works really well and would be exactly what we want here, plus it handles all the movement nicely.