Look to the Levittown experience for how variation is a naturally emergent property in the right setting; identical houses stamped out assembly-line fashion, yet after a decade they were already adapted to the point it was becoming difficult to discern houses on the same block started out identical to each other. The key was a design that was very open to owner adaptation.
Housing affordability is complex issue. While there are local factors like zoning as you mentioned, artificial distortions in the open market for land in the US (and much of the rest of the world) contribute a plurality of the effects causing the stratospheric cost of land wherever well-paying jobs can be found.
For every Levittown there are also hundreds of neighborhoods that never got any better after they were built. I would argue that Levittown can't be disentangled from the economic period in the United States - and it reflected the improving economic position of the working class. That ended in the 1970's for the United States (the GDP kept rising but it has gone to the rich. And home ownership is the same percent right now as it was in the mid-1970's.)
Going out on a limb, I think yourapostasy pointed to Levittown not to attempt to explain the entire economics of housing for the U.S.A. during the 70's (because hey, if we're taking the issue to that level we have to talk globally about inflation, oil, etc), but rather they were simply suggesting that, given the (in yourapostasy's ,i think correct and understated, words) "complex" issues surrounding affordable housing, Levittown is a helpful example in as far as providing a cookie cutter foundation which lends itself to indiviualisation over the long term, which is actually a more complex concept (much like building mountains or clouds out of simpler fractal shapes) than it first seems.
On point. The complexity of the overall land affordability issue isn't amenable to deconstructing in this forum's format, but yes, individualization is cheaper to accrete over time than build in from the start (especially if the labor input costs to generate the "individual differences" in the initial designs and operational implementations is driven by land costs themselves).
I agree that variation can emerge, but still wonder if it can be built in from the start. Do we really want to wait decades for our neighborhoods to gain individuality? Will Levittown ever reach the richness of some of the most beautiful cities?
What other artificial distortions are you thinking of?
Variation can be built in from the start as long as you are willing to pay for it. It is cheaper at the initial design and implementation stages to stamp out identical units that are openly adaptable. The architectural community's exploration into design patterns that filtered over to our community's GoF looked into a lot of these and related issues. The richness achieved over time was arguably very beautiful, as long as you placed a premium upon deep-rooted community identities built out of decades of individual adaptations, emerging like a coral reef.
A full discourse on HN isn't really the right format and forum to discuss land and socioeconomic policy, unless in the context of programmable shelter construction or similar. So I'll offer a tip of the iceberg thumbnail sketch. Land as an asset is given special privileges that other assets do not enjoy, and tightly coupled with that is debt (leverage for land) and capital are treated with special privileges that also are rarely found in other asset classes. These privileges are often enrobed and justified "for encouraging economic growth and development", but while that was true at inception, reflexivity has rendered those rationales moot today.
Personally, I've studied enough to realize I don't have the power to materially change any of this, and instead I focus upon what I can change in my individual sphere of influence. For my personal setting, that means focusing upon modular, incremental improvements in opex and deliberately eschewing conventional norms of how to allocate capex. A concrete example is eventually spending more on foamed glass insulation over time as the original shell itself, with the realization that easily-maintainable 70+ R-value insulation over >100 years between replacements will pay for itself on opex savings alone. A tangentially-related concept is reducing the economic churn in your and your family's lives as a means towards the cost avoidance of the associated economic rents extracted from the churn.
Housing affordability is complex issue. While there are local factors like zoning as you mentioned, artificial distortions in the open market for land in the US (and much of the rest of the world) contribute a plurality of the effects causing the stratospheric cost of land wherever well-paying jobs can be found.