This would answer your second issue; the voting one, by allowing those who cannot remain within an area they'd like to live in long enough to meaningfully vote in that area to vote in the general state-wide process specification level which would then have more local effects.

Experience in many parts of the world has shown that this is very much not true. A few examples:

- China: the history of the past few decades has very much been the history of demolishing slums because they're too dense and building much more expensive housing on top of it. You can make arguments about the housing bubble there, but slums are being demolished, not built, and affordability is still very much a dream (partly as a result of state policy, partly other factors)

- Singapore: as a city-state, city zoning policy is national zoning policy. The mandate is very much public and affordable housing for all, and local control over zoning is non-existent. The HDB's job has been pretty much demolishing slums and turning them into public housing.

- Malaysia (my home country): local municipalities have a small degree of control over zoning policy, subject to national control and state oversight. Same story here: there is a systematic effort to demolish slums and turn them into high-rise developments (partly because the zoning authorities have been captured by the developers). They reluctantly follow low-income housing quotas due to politics too complicated to explain here

- Japan: localities can only do so much, the story of Tokyo (same for Osaka and Nagoya) has pretty much been a story of top-down national control with the explicitly policy of managing urban density. Same story with a concerted effort of demolishing slums.

So your claim of either slums or high housing prices doesn't really happen in reality. If you have examples where this happened, please do share, but having lived in many Asian cities this doesn't bear out at all.