We have tossed around similar ideas. We've talked about a "World at War" terrain representing all major theaters. ETO in the west with appropriate German British and US equip etc. Islands on the east side with USN and IJN carriers and such.
south MTO, north Russian front.The map would have to be huge and chopped and spliced leaving out large world portions. I'd like to do such a map once I really learn the TE.
One of the problems we have are that finite numbers of AC can't be enabled, meaning that we would have to manually keep track of the numbers destroyed and manually disable them at the right time.
People also might get sick of the same map for so long.
Concepts like this are harder for us to do than you might think with the tools we have, but are certainly worthy of discussion, we might find a way to do something of the like.