Please make the seats comfy!
This may already exist in larger, more modern aircraft, but GPS (and other systems that rely on having up-to-date databases) should be remotely upgradable. My digital radio can upgrade itself over the internet; how about my GPS being able to grab the latest Jeppeson without having to unplug it and send it off to the manufacturer? This could be as simple as a 3G SIM card, allowing an internet connection via the cellular network.