1. When I see an expression like "This scene needs X characters" I always ask myself "All at once?".
One trick in wrestling that's so famous people don't even see it happening under their noses is "spooling in wrestlers during the match". Four people are in the ring. Some guy #5 wants to be in the match but that's too many people for the choreography. A member of the original four will take a hit and fall off the ring apron. He will proceed to lie on the floor while #5 interacts - it's still a 4-man fight until someone gets eliminated (usually #5) and then the guy on the floor will rejoin the match.
Another trick wrestling uses is to break the unneeded opponents away into a simple brawl at the side of the ring while the main participants continue the match. You (the choreographer) may add as many extras to the minibrawl as you like. It doesn't matter what's going on down there - only matters that punches are being thrown and some combat occurs. The voice announcers will not discuss the brawl until some winner emerges and rejoins the main event.
2. I've learned over time that I can only take three new names per chapter. After that it's just so&so, son of so&so. This averages across chapters, so if chapter one contains 9 names, I should have them all straight by chapter three. You can safely exceed this limit. Return of the Jedi did in its final battle. For me it was just so&so in an XWing and so&so in another XWing. I don't think Lucas cares if I can't name the 3rd guy on the left five minutes after watching the movie.
3. I've heard the dog-fighting complaint before, but it's the future. Fighter craft can still chase each other. Sure they don't need to "bank" as they turn, but they can still turn. And they can try to get "uplight" of each other so one side a quarter second behind due to the speed of light. The guy who's behind is gonna have a harder time scoring hits.
In the VQ stories, Firestarter is in a ship that is braking in space, and a reviewer commented that ships couldn't really brake in space. This is true for "current" ships - they just plow into the atmosphere as full speed, but the Enterprise had to problem coming to a dead stop.
Net point: If you deem your ships will maneuver for tactical advantage, just go ahead and do it. Maybe just don't call it "dog-fighting" so people don't get confused.