I can see needing 9 to 12 channels, possibly more, for for an extremely scaled out WWII bomber.
Off the top of my head
1 or 2 ailerons
1 or 2 flaps
1 elevator
1 throttle, possibly more for 4 engines
1 landing gear
1 bomb bay
1 bomb release
1 lights
1 per gunner turret

Since it might be a few years before you are ready to build and fly this monster I do not think buying a radio for it now is a good idea. Radios change so what you think is future proof probably isn't. In a few years, who knows what will be available? The current whiz-bang 2.4ghz stuff may be 'old news,' replaced by something even better.

If JR is your favorite, you can get an XG6 for about $230, and go for the thousand dollar plus unit later.