Honestly, there doesn't seem to be a ton in that base that would serve as a disincentive to restarting. (i.e.: It doesn't appear you have 1800 decorative objects, etc.)
But a lot of us can empathize with having an "oh boy, I have to start over again, don't I?" moment.
Generally, if you want free reign to do a comprehensive upstairs / downstairs layout, you go with a 24x28 plot in which you drop a 24x24 room.
Then you can repack that 24x24 space into however many rooms you want as depicted in the below example. Bonus: No more actual doorways with lighting issues, etc to deal with. Penalty: You can't use a bunch of different tilesets (Arcane vs Industrial vs. Tech vs. etc) if you build this way.