I think marina operators should look very carefully at the mobile home and caravan legislation before contemplating residential moorings. Once there are a significant number of official residential moorers, there will no doubt follow a campaign by some of them to have the same rights as mobile home owners do. Which include very controlled rents, extensive, nigh on permanent, tenancy rights and plenty of obligations on landlords.
If I were a marina operator, I'd be thinking along the lines of £n thousand pounds per annum for someone whose mooring fees I can increase as I want, kick off at the end of the agreement, and have no obligations to beyond that in the contract compared with perhaps twice that for all the constraints that come with residential moorings. Only the desperate amongst marina operators are going to want to go down that route.
With mobile homes and caravans, the landowners get profit from sales, with boats they can't.
Never mind what the councils think of it, I reckon the marina operators won't be interested.