Well, the riding you can't do on the 5 acre lots, unless you stay in an arena, which is pretty boring 24/7. The rest is fine, as you can't support horses on most land around here unless you have LOTS of acreage. Every one feeds hay, instead of depanding on grazing. In Albuquerque, they have a long history of agri-areas, and run more horses on a smaller acreage than I've seen anywhere. Commercial stables/trainers/breeders operate on 5-6 acre lots. In the city!
The communal stables is a good idea. There are very few 'equestrian communities' around here.

(One has a fairly large event center.) There's one or two in the works, or were in the works, which are VERY high end.