Imagine apartments built into what used to be department stores, (Oh, you’re JC Penny 203? I’m at Sears 106). Get those old arcades up and running. Set up meal stations at the food court. Once people actually live there, stores will start to move back in.
If I’m unable to finish my life in my own home, that doesn’t sound like a terrible option.
This is the answer.
A cheap / half assed conversion would be a ghetto. It would be awful.
Sanitation would be a huge problem also. In an apartment you have access to air from the outside. Imagine everyone living in a box in the same enclosed space. Yes I understand malls have gargantuan (and expensive) air conditioning systems. It would still stink.
Not to mention the money. Even a derelict mall is still worth many millions of dollars. You have to buy or lease the building from them.
You’d be much better off creating a walkable community of low-cost housing in a low-density semi-rural area.