We need 3 slots because the random pilots look like they've had too many generations of reproduction with their siblings and cousins.
After about 30 hire fire's you may have one pilot that looks "average", meaning that if you've had twelve pints in the pub you might let it enter your ship. The second slot is used up while playing the pilot roulette to hold any potential cases that might replace your average one. The last one is needed to keep the roulette wheel spinning. After a thousand tries you may find one that isn't a blue haired LGBTQWTF that fell down from the roof of a Type 9 and got only slightly disfigured upon hitting the landing pad.
That's why no new content is needed
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Although, like was said said earlier, being able to equip NPC's as modules would be pretty nice and I wouldn't mind seeing them stay in the ship as long as they're not unequipped (for QoL) and only leech money at their normal % while the ship is in use. I can think of a few different jobs for them such as pilot (same as now), mechanic (could attempt to fix modules with engineering materials and duct tape, could also allow salvage missions if there would be any kind of salvage game play in the future - e.g. go salvage Jameson's Cobra with the help of some specific mechanic that knows how to make it running again), Eye Candy (just look pretty while sitting on the adjacent seat - to make it authentic you lose half of your assets if you fail to complete whatever Eye Candy needs). Mission NPC's (some nagging snob sits there instead of Eye Candy and tells you to go see Sag. A but also wants you to fetch some snacks for the pooch - perhaps it's time to check if the airlock is still functioning). Also while there is no ironman mode for players they could just fix NPC deaths by increasing the insurance cost by 5% per crew member.