Supermarkets in a different class?

According to the BBC, Bristol City Council and the London Assembly are calling for a new supermarket classification in planning law.

The argument is that the impact of supermarkets on their local areas are different from smaller independent retailers. For example, supermarkets require frequent deliveries from heavy goods vehicles. Putting supermarkets in a different class would allow the land use planning system to manage these externalities when a firm wants to open up a new store.

Clearly there needs to be a mechanism to manage externalities from development. But I would make a few points. First, the growth in "metro" type stores has been partly driven by planning restrictions on out of town developments. So, restricting out of town development means the externalities of frequent deliveries are felt in city centres. Second, delivery to stores followed by sales to consumers is a mechanism of distributing groceries to consumers. If supermarkets don't do this then some other mechanism would be required. What is that alternative (e.g. larger independent stores with more frequent deliveries) and are the externalities any different? Third, if the planning system is changed how could we be sure that change of use decisions would only be used to manage the externalities created by supermarkets rather than allowing particular groups to block development that they don't like?