To be reasonable, if you want to run a car like this why not run it with the HSCC? It is after all their class and club.
I can see the FIA legal point, but not everyone wants to spend that amount to race. If you don't like the class then don't enter. There are plenty of other places to race an FIA car unless you consider the other places to be "bent" in which case the argument is self defeating.
I really think it is close to what was known as Group 5 touring cars (1967) and as such I'd be more inclined to complain that they don't allow Porsche 911s rather than ask them to restrict themselves to FIA App K. This class has a rightful place in history thus it follows that a club with "Historic" in its name would be a logical place. Of course if the other word was "Sportscar" you might have an argument but as that is no.................. Oh wait!
Superspeed Anglia anyone?