I don’t think the goal is to increase the apartment capacity of existing multi-stair buildings.

Allowing single stair buildings facilitates multi family dwellings to be built on much smaller lots - even those that currently contain single family homes.

Changing that regulation is the basis for why cities like Paris can’t maintain New York level postulation density without many buildings greater than 6 floors.

Good point: I'm in a suburban area where land is much easier to come by, so it's less of an issue. Although even then, 3-bedroom apartments are as rare as... Something very rare. (It's Christmas, metaphors fail me at the moment.)

Anyway, if they built floor plans like this then I would want to see some seriously bulked up building codes to deal with fires. Also it always strikes me as odd that sprinkler systems are used to help with the fire, but smoke is what mostly kills and I rarely hear of emergency ventilation systems tied to fire alarms. If anyone knowledgeable on that sort of thing could chime in, I always love to learn why my ideas are wrong/bad.