If they are serious about space efficiency, they should look at layouts Soviets developed to "warehouse" their citizen in - no luxury, but it really worked magic with efficiency.

I grew up in 33 m^2 apartment. Layout is similar to this, minus the balcony: http://cdn.gdeetotdom.ru/b/b9f1203ec7061e6dc65984ff104ecfb7-...

The major difference is that you have a separation of space with the kitchen and hallway (with closets). That separation made it fairly livable for a family with a child! (Don't recommend stuffing a teenager in there, but it has been done...)

The completely open studio layout will likely not be great even for a couple, as sometimes your really do need space or privacy. A blocked off kitchen affords that and doubles as a decent home office.

I don't recall us resorting to space-efficient furniture, but then again Soviet furniture was smaller already and I did sleep on a foldout couch.

For entertaining, that tiny kitchen actually fit 5-6 people reasonably well. I think our informal record was 14 (3 standing, rest comfortably seating).

The kitchen became such a part of the culture as a place to sit down and talk privately, that there have been articles and books written about it. It really highlights the genius utility of that small extra space. Unfortunately, all I could find in English is a really terrible NPR article that shows a place you'd need a hasmat suit to enter as a "typical" Russian kitchen... Still the utility is amazing!

EDIT: as discussed below, Tokyo calls such layout 1DK (with 2 rooms effectively, 2nd being the kitchen). These are much more desirable than the 1K true studio apartments.