AND, the LG is required to consider parking, setbacks etc under "constraints" analysis of the HA so this gives advocates a 2nd bite at the apple to make cities do this analysis - once for zoning capacity, and then again for constraints.

It's not clear though how meaningful HCD's oversight will be on constraints. If you look at this sample site analysis, for example, you'll notice there is no analysis of regulatory (as opposed to environmental) constraints.

I might urge HCD to consider a similar "safe harbor" formula on constraints. Eg, if parking mins use up less than a set % of FAR, it's not a constraint. A parking space generally takes up about 320 SF of space. so multiply x number of units to get FAR that's taken up by parking

Chris has a great paper where he argues that cities should be deemed "presumptively constrained" under the constraint analysis if they fail certain benchmarks, but those benchmarks might not work as well when the q is whether a particular site has zoning capacity.

EDIT: 3) The memo prescribes the use of "by right" zoning in certain circumstances but outside those circumstances it's unclear if cities can use discretionary mechanisms like CUPs.

Suppose a site is zoned for 30 du/acre but you need a CUP to build at that density. Can I designate that site for moderate income housing without a rezoning, or do I need to rezone to remove the CUP requirement? That's unclear to me.

If city has to rezone to achieve adequate capacity for lower or moderate income housing, the rezoning has to provide for by-right development of 20% BMR units. By-right is also required for "recycling" of non-vacant sites from previous HE.

But I guess my question is, does the city have to rezone to achieve adequate capacity in the situation I described, or can it argue that it is already zoned to acommodate the housing?

Yes I'd be pretty surprised if potential ADUs were credited to lower-income share. Moderate maybe. Whether city has to rezone depends on total capacity under existing zoning.