We've had our current development code for over a decade now and (unlike the previous) it stresses the grid pattern, block size, connectivity, homes (single and multifamily) fronting streets, etc. In the late 90s/early 2000s, when we had 100+ acre greenfield sites being developed, it resulted in the construction of several subdivisions that I would characterize as being new urbanist in nature. I live in one of them, and thoroughly buy into it.
Now, in our life cycle of our town, we're in the situation of the 100 acre square shaped parcels being mostly gone and infill of irregular shaped parcels of around 25 acres being the norm. These parcels are usually surrounded by older PUD type subdivisions where there's no pre-existing gird pattern to connect into. Parcels shaped like a five pointed star with two ditches running through them and topography similar to Patagonia (slight exaggeration). There's brain damage that occurs in trying to make these parcels meet grid pattern, block size, and street fronting principles for all the units, further complicated by the surrounding neighborhood finding these design concepts too foreign for their existing conditions.
My question or thought is this: Are there communities with new urbanism type design codes that allow flexing away these codes in the case of "infill"? If you have 100 acres and/or a square shaped parcel, you design one way; if you have 20 acres shaped like Chile you can design another way? I'm not a planner, but an engineer, so my apologies in advance if I misrepresent aspects of new urbanism as I understand them.