I'm with you, a reasonable middle ground like that is a great way to go. I visited Nagoya and Tokyo and was very positively impressed with the kinds of neighborhoods generated by that kind of zoning. In a way, the typical pattern actually generated more diversity YET more solitude and peacefulness than I see in the US.
Here in the USA, only the older parts of the old pre-zoning cities have a shot at being nice like that, and even that may have been ruined in many cities. I think we artificially have an obsession with preservation in the USA, because current zoning means that many building forms are unbuildable today so the only way to get them is to preserve something old. These nice old sorts of buildings and neighborhoods can be destroyed but not created, but that's only an artifact of zoning. With more Japanese-style zoning, preservation would be less important
So there is a more healthier and lenient alternative to city planning which does not result in total chaos. I think many people here are stuck in between two extremes. The anarchistic what ever goes crowd that's sick and tired of the bureaucratic mess, and what we currently have. However there is I think a healthier synthesis between the two ideas that we need to really consider.
We know what the problem is, we know why there's a problem, and we even have plenty of solutions, but as has been pointed out the problem is in implementation. That's the real problem.
Here's the full post: http://urbankchoze.blogspot.ca/2014/04/japanese-zoning.html