I'm sure it can be done with a modular workflow. I would make modular pieces for the interior walls, floors and ceiling, and then a second modular kit for the exterior entrance. Or just make a unique mesh for that side of the building.
The Pool room concept looks good. How would the layout be constructed in a production environment? Usually, a pool room like this would be enterable from the exterior so I'm not sure if there is any modularity involved.