Sounds like a good idea.
So, it seems that being able to define orbiting parameters is just what we need.
I'd propose another thing for that, +Orbit Facing: This would be a vector which orbiting AI will try to turn towards it's target. For fighters, it should be 0, 0, 1 (and it should default to it), but for bigger craft, you could set it so a ship will try to face the target with it's best armed side. Perhaps you could even define multiple vectors, so the ship would try to turn to the nearest one.
This would pretty much make capship attack orders a viable option.
If we could also allow "Stand Still" command to be issued by the player, commanding capships would be surprisingly near Nexus, as commands like "run away", "move to" and "protect" ("keep safe distance" "stay near ship" and "guard" respectively) are already in FSO, they just need to be enabled.