Pulling this from the other thread and responding here, to try and make twincitizen happyI generally agree with you this is how it should work, but in many cases you're going to run into problems with too many different zoning levels and not enough space. There's just too many levels of commercial to step down all the way from C4 to R whatever without taking up a huge amount of space.A few changes I'd be OK with:
Zoning has to be contiguous. If you wanna upzone or downzone a lot, you have to also rezone every lot on that block (or maybe every lot facing the same street on that block would be more appropriate, but same difference).
Zoning has to be graduated. R1 can only border R2 can only border R3 etc etc. R1 can only border C1 or C2, R2 can border C1, C2, or C3, R3 can border C2, C3, C4, R4 can border C3 or C4, R5 and above can only border C4. You can move those boundaries around a bit but the general point still stands.
It'd be an interesting experiment, start with the most intense uses, and stepdown from there, and see how much of the city would be forcibly upzoned with my scheme.
But I may not have been clear, residential and commercial can be next to each other.
As it currently stands, for residential, there are 6 types of zonings (R1 vs R1A and R2 vs R2B are close enough to be lumped together). R1 and R2 are classified "low density," R3 and R4 and classified "medium density" and R4 and R5 are classified "high density." I'm not super familiair with the current Commercial zoning, but I'd bet you could easily classify them into "low," "medium," and "high" intensity. (My first instinct would be C1 and C2 are "low," C3A and C3S are "medium," and C4, very rare, would be "high" but it may be the case that the commerical code is stratifying on use not intensity, in which case who knows, it'd all have to be redone for this scheme). Everything in the Downtown zone would be considered "high." Office residential seems to also be more concerned with use than intensity, but at a glance I'd call OR1 "low," and OR2 and OR3 "high" (there would be no "medium" office residential). Industrial I'm not really sure about, other than to say that "light industrial" should just be folded into commercial, and then there should be some kind of separation of medium and general from other zones, depending on actual use of the facility.
So, now that everything is "low," "medium," or "high," it becomes quite simple. Low can be near low or medium. Medium can be by low or high. High can be by medium or high. You'd experience a general gradation of intense areas into quieter residential areas, and if demand ever intensified, zoning would adapt to accommodate that, rather than every new building being a fight.