It seems to me, the answer is a national law that requires councils to look favourably on planning permissions for eco friendly buildings with an eco friendly lifestyle, though with a proviso that such homes/lifestyles have an annual check to see they still meet the criteria.
In this way, if you want to build a wooden house with sustainable,renewable technologies and farm / breed horses / work wood etc. in the countryside then you would be able to do this, while stopping those who just want to build a cheap house and put in a great big petrol generator and say they are ‘off grid’.
It would make sense to have some kind of proviso for having to live there so many days a year, to stop it being a 2nd home scam for city dwellers.
I remember seeing some woodsman on tv who got permission to build a wooden house in the woods as he needed to be onsite for charcoal production but not be able to sell the house and if he wanted to leave, would have to return the land to its previous state, that seemed a fair ruling to me.
What do you reckon ?