The current SP challenges are cool, but after they are beat, it doesn't really feel that fun. My idea is to have a combat challenge (or a series of them, rather) where you start out with a challenge similar to the WWII dogfight mission (no jets or missiles, etc.). As each mission progresses though, the enemies get more viable and more parts can be used for your own aircraft. Maybe there will also be parts of the campaign where you have to sink ships or attack ground targets. Or maybe a mission where there is really heavy winds or fog? I think that it would be a fun idea.