I've been fiddling on and off with something similar. The Pacific War rages in my Golden Wings and eventually the southeast of England will also be at war.
The Donationware F4U Corsair package, available here at SOH, includes two very nice American air bases in the Solomons.
Bill Lyons' Classic Goose package includes a couple of Japanese bases in the Marivellas - plus the fictional Marivellas Islands themselves. It's supposed to represent a slightly pre-war time period, as in the late lamented Cutter's Goose TV series, but the AI Bettys and Zeroes are of wartime vintage.
There is a nice Midway scenery with both pre-war and wartime options (can't recall who made it.) There's also a scenery of the Marianas in 1945, complete with AI B-29s (can't recall who did that one either.)
In addition to the British bases mentioned by others, there's a scenery of the USAAF base at Middle Wollop, England included with Dave Eckerts' Martin B-26 Marauder.
Someone released flak over Germany, and again I don't remember who.
There are a couple of RAF bases included in the first one or two updates to Golden Wings, complete with AI RAF Hurricanes and Spitfires in early wartime camo and markings.
Everything I've mentioned came from either FlightSim.com, AvSim, SimV or here, since those are all the sites I get stuff from.