What John said.
IMHO, if you (or anyone) ever find yourself thinking along the lines of your idea #3, step back and think some more about stories.
I don't understand your comments for #1 and #2 ... putting the mezzanine on another story has no effect on the elevations / model ... unless, as John suggests, the walls/windows were not modeled correctly.
Do search the forum for multistory windows ... the thread may come up. Depending on the situation, a story-spanning wall may work, but often bits of wall on each story are needed with windows in each, and in the case of the spanning windows, a 'wallhole' has to be inserted in the wall that is covering up the window so that elevations/model come out OK. (There have been many wishes/complaints about this need.)
Karl
One of the forum moderators
AC 28 USA and earlier • macOS Sonoma 14.7.1, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB