Hearing "Skeleton Crew", since that term is used a lot, instantly bring to mind that this is the number of crew member the ship needs to work. Hearing though "Base Complement", confuses me a bit, making me wonder what that could mean. If the term was "Crew Complement" or "Base Crew Complement", it would bring to mind that it talks about the crew, so even if I did not know the naval term I would understand it is about the crew.
Same for "Passenger Capacity". When I hear that, I imagine that even normal civilians can board the ship, acting as mere passengers. Sure in civilian and crew transport ships it might make sense, but for the rest wouldn't it make sense if it was "Crew Capacity".
As for additional crew providing no benefit, I think you are wrong here. In battle crew member die, be it from rough battles o from fighters not making it back. The moment these crew members die, the ships become understrength. Maybe in small battles it is ok to go out with just the base crew needed, but that is only in the beginning. Sooner or later, taking just enough crew to go for battle, is just not an option.