Costco--but with 800 apartments

[tomh009]

I think it would be quite hard to retrofit existing locations… modern warehouses are truly the simplest steel boxes you can build.

Quite true. But because they are so simple, it would not be difficult to add concrete columns and/or supporting walls (to support the upper walls) without massively disrupting the basic warehouse steel/concrete box. Essentially the ground-floor warehouse would be as is, you don't use any of it for supporting the upper floors, instead building the supports either just outside the existing walls or in the interior of the existing warehouse.