There are plans afoot to put in a northern Norwich by-pass,which will probably make some road travel easier.
Even so,I can't see Norwich airport ever becoming much more important for air travel than it is now.
Surely the most sensible way forward would be to see how commercial air traffic develops over a period ,then if does then become neccessary to have Class D,forward the proposal at that time.I have travelled a couple of time from Norwich,once was direct flight and OK but the other we routed via Schipol which was a pain.
Stansted is not too far away from Norfolk and has good connections to most destinations,it is my choice whenever possible.
Lister