There seems to be a woeful lack of original thought given for model aircraft designs being requested.
The aircraft that never made production would give a bit of variability.
Consider TSR 2.
Gloster E.28/39. first British jet,
De Havilland Vampire.
Hawker 1154.
Horten Ho 229
I have a war time observers book that lists the DH Mosquito as a prototype.
However there a mass of drawings of types of German float and flying boats that seem to have been lost to the model world.
Surly there are better ideas than Spitfire, Me109, FW 190 & P39