First of all, I'm echoing the idea of a Dunkirk map, and I have two idea's of my own if I may be so kind;
1) A England - North Sea - Netherlands map (roughly the area north of the current game map). This area saw extensive action from 1939 to 1945, so it could prove a worthwile project to invest your time in. For online purposes it would be great to scale this area down, by slimming down the sea between the land masses, much like IL2's Norway map.
The Air War over Holland has been researched very thorougly throughout the years and a lot of research material is easily obtained, which would certainly speed up the process. Building wise, by mixing the English, French and German building sets could provide very satisfying results.
2) An early MTO map
A map of Greece or Malta or such will be of great value breaking up the monotony of flying over the Channel
Thanks.