I agree the problem is with the SEB and the current rules.
However I disagree with your logic that all sevens ar mods of a Ford.
To follow that logic then all 911s would be mods of the first Porsche. Not distinct modles.
There were four distinct variations of the Seven under Lotus and a few more under Caterham. Each modle could be recognised based on published standards from the manufacturer. That I think can be said of most other Sevensque cars like Birkin, Westfield, Stalker, Ultralite, robinhood, Tiger, etc.
It can not be said of the locost cars because there is no production standard or list of required components.
I think therein lies the problem with the rules.
Michael D.