With potentially more and more info about each system, maybe it would be nice to be able to pass something with the filter that tells the API what info we care about.
Something like ['coord', 'stations', 'celestial'] to tell it we want the coordinates, a list of stations, and a list/tree/??? of celestial bodies.
Or even more detailed like { 'stations': ['orbitting', 'services'], 'celestial': ['stars', 'planets', 'moons', 'asteroids'] } if we want to know which body a station is orbitting, what services are offered, etc...
Celestial bodies would be nice, but for most purposes I can think (trading or bulletin board missions) of only the stations are necessary, so I wonder if anyone would spend the time to provide the data (unless there is an API of course). The systems.json format upon which my own one is based (or likely both formats influenced each other really) lists station names, distances and services. A single distance value for the station seems to be sufficient, its the magnitude of the value that seems to be relevant anyway. I use the same format for backup, storage on bitbucket and in the communication between the server and the web pages.