So, it is about rebuilding whole infrastructure from the ground: public transport, walking, biking, office spaces, not just building high condo complexes.
- LA is already building various large expansions of public transit, as well as walking/biking infrastructure.
- Generally the shops basically come along with the housing. "Activating" the ground floor - putting retail or other public uses into the ground floor of buildings that are residential above is standard practice when building those taller residential buildings along main arteries, on busy corners, and so on.
which suffers from many difficulties and cost overruns because of existing layout.
I think it would be more cost efficient to build another city/town nearby from the ground, and people decide where they want to live given differences in cost and lifestyle.
That is ignoring the fact that in our perfect city above, just a few years later we will discover something new we forgot to account for and now our city is imperfect.