Its better to design a well designed two bedroom house in a back yard than a badly designed big shed. Accessory dwelling units – and yes even permitted development rights rules – should allow for this. Who care if you have to enter through a house if the back yard is wide and deep enough. They can be used as granny annexes. Airbnbs avoiding loss of the main house to Airbnb, houses for members of the extended family, avoiding kitchen and bathroom sharing. As long as they are no more than 5m high, have a footprint no more than 2 sqm and are at least 15m from the nearest habitable room window of another house they should be allowed under ADU zoning rules or PD (subject to prior approval rules).