Costco--but with 800 apartments

[Bytor]

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.

Warehouse buildings like that are generally designed for a 30-year lifespan. At that point, the escalating repair costs are not seen as worthwhile and the building is either torn down and a new one built, or it is gutted and completely refitted. That refitting, though is almost as expensive as a new building from scratch.

As such I am not sure that retro-fitting to be a pillar base would be a practical or viable option.

There is also a Costco in Vancouver right by the Stadium-Chinatown Skytrain station.