Brendon Harre spells out the case for formalising neighbours' Coasean bargains. He argues we should all be able to build up to three stories by right, with provisions against encroaching on neighbours' sun, but with better ways of mutually waiving those provisions.
Neighbours can always agree to not object to each others' encroachments into recession planes. But you then can have a sequencing issue. If I agree today to allow you to go up to three stories and block my backyard sun because you're agreeing to let me build up in the back yard anyway, that's great. But if you then sell the house, your agreement doesn't move with the property. And so I might be reluctant to agree in the first place - unless I can get things lined up to build quickly as well.
I think this idea came originally from Stephen Franks. I touched on it in my piece at The Spinoff; it's great to see Brendon laying out more of the details.