bruto
Penultimate Amazing
Continuing on the "what could go wrong" level here, I'm reminded of the disappointingly bad movie "Snowpiercer," which did have at least one point, which is that in a linear society it's pretty easy to isolate the underclass. Of course that's possible anyway, and every city seems to have its slums and favelas, but it seems likely to be especially easy to do by initial design, if the city is enormously high and enormously long. Put all the low ranking housing at the bottom of the far end, or perhaps at the bottom of the middle, with the mass-transit equivalent of servants' staircases to get them to their destinations. In an enterprise this huge, and this complex, I suspect it would be very easy to engineer in durable system of social stratification, with transit, social services, etc. separate.