Those all sound good,
Always need a good excuse to build Spitfires and Me 109’s
For Ost front you could base it on campaigns for dates, seems like it would be a good cross “genre” build to include aircraft, armor, figures etc. So you could do a Barbarossa build, Stalingrad build, Kursk build etc.
I’m working on space exploration kits for my son’s room, X-planes fall right into that catagory.
I had an idea for a couple too…
I was thinking about a “got a new job” build equipment being used by new owners, civilian conversions of military equipment like firefighting Air tankers from old bombers, fire engines from military trucks, wild 4x4 Willy’s jeeps, air racers, second hand equipment under new colors (Isreali Shermans, South African Comets, captured equipment etc). Basically any equipment not being used by the original owner.
I think a North Africa build would be fun too, lots of unique things from the desert plus its the best chance to build Italian stuff.
A nightfighter / stealth build could be fun, again lots of aircraft that don’t get the same attention as their day fighter counterparts.
and finally I thought something based on the Korean war era could be fun, lots of cutting edge (for the time) equipment that doesn’t get much attention compared to WW2, Vietnam and modern.