Good point about the RVs or trailers.  Metro Vancouver already has/had this housing model, and last I looked almost every trailer park or year round campground in metro Vancouver has closed so that the owners could capitalize on developing the land. 

You could park an RV/trailer on a driveway or in the backyard and use it as low cost housing for rentals or family. Bylaws say no. Instead of re-inventing the small housing unit, we could legalize trailers, mobile homes et al to infil space on residential land.

I suspect the "cute and trendy" factor is missing from a parked trailer as opposed to a tiny house.