Great question, there are bunch of scale kits I always wanted to build.
Old Top Flite Form Flite scale models are pretty small, but good flyers if kept light. The Mustang is the best as it is the biggest. I think a modern 25 R/C engine would be great. The P-40 and Thunderbolt are good, probably best powered with 09's. I have a couple, yet unbuilt.
My eldest son built a Nats winning Focke Wulf from a Guillows 27" (3/4 " to 1') kit, he sheeted it with 1/32nd and it was powered by a Fuji 09 R/C with a JRoberts three line bellcrank, so all of the larger Guillows kits are possibilities.
My scale stuff is from 1/2A to 60 sized. Consolidated F4U, Typhoon, Stuka, Mustang, Zero and Focke Wulf. Scientific Beechcraft, Sizzlin' Liz Mustang, F-82 Twin Mustang, etc. Enterprise Caudron, and stuff like that. The old 35 sized stuff I have is the Capitol Beechcraft, Sterling Monocoupe, Mr. Mulligan, Corsair, etc. I'd like to build clones of my collection of Berkeley Swee' Pea, Minnow, Shoestring (as B TR's first) and Little Stinker, too.
I am researching for a P-39 Airacobra from the old Red Box TF R/C kit. It is going to be a major redesign of the nose, but then what is easy about building kits? I guess it is going to be more of a guide!
My new Old Time Stunt model is scale too. There are a ton of old plans around that have potential for OT.
I guess I want to build a lot of models, I better start cutting wood.
Chris...