Class D is generally though not always 4 nautical miles not 5, which is a 20% smaller area.

Now, if you want more permissive rules around class D airspace that's IMO very reasonable. But, talking about class B as any airport is extremely misleading.

PS: Class C is again not that long a list, and still represents high traffic areas: https://en.wikipedia.org/wiki/List_of_Class_C_airports_in_th....