Adding to the list of facilities all major airports should have is a left luggage office. This is one of those services that in many places has been discontinued in the name of "security". Given that airports like London Gatwick and Lima Jorge Chávez have managed to keep their baggage storage offices running in the face of rather extreme terrorist threat--the ones at Gatwick have luggage scanners to make sure you're not trying to store explosives or something--I wonder about the "security" excuse.
Left luggage, showers, sleep cubicles...there are probably lots of other features I'm forgetting that would be really useful to have at an airport. I mean, aside from the basic services airports generally do provide.