When you taunt the enemy Rapiers, they're always Kilrathi pilots. The game seemed to imply that humans were being forced to still run the ship in some respect, though.
Maintenance, probably - human fighters would not be designed for ease of access by Kilrathi mechanics. I'm betting they'd need to refit the cockpit or recruit some rather weedy 'Cats for pilots as well.
Yeah, there's always the joke about how the Kat ships have holes in the seats for tails, besides the fact that a kilrathi is a lot larger than a human. The cockpits of terran fighters probably feel pretty cramped to a Kilrathi.
I actually think that either Flint or Cobra deserve a slot on this list - female pilots certainly have the potential to be far deadlier, (if you study even a little bit of female psychology)
They are extremely intuitive, can multitask naturally (able to track several fighters or pursue a target while evading oncoming dangers) etc.
Females are better pilots as they can handle higher G-forces than men
Moot when you have artificial gravity (or 'acceleration compensators', heh)
As for Hobbes, I imagine the Confed fighters that he was qualified for have roomy enough cockpits that a custom seat for him would fit without *too* much trouble.