I think I've figured out the wingmen in Crimson Skies. They're not actually there to help you, like you would expect -- they're there to give you more obstacles to run into (to add to the challenge of the game). That explains why they're constantly zooming across in front of me (when there's no enemy aircraft there for them to attack), or jumping into my line of fire when I finally get an enemy craft lined up.
So, note to myself: wingmen = avoid.
That doesn't help with the maneuvering, of course, but we'll get to that later.