Why? I think some players want to empire build and some want to have a place that they can customise and call their own.
How it would work? Probably not in a way that could become a credit generator for the player, more a credit sink. I did post on the suggestions forum a long time ago an idea about players with shed loads of money spending that on securing a planetary base and then spending even more money to add facilities so other players can come and refuel, repair even buy ships - the profits from such actions would not return to the player, just contribute to the factions in system.
Where would the people come from to fill the positions? Jobserve or the 34th century equivalent ;-) The total population of the bubble is many trillions, so having 400 or so rock up and perform docking functions for a player wouldn't be too far of an issue, providing you pay them enough! ;-)
The real challenge is BGS interaction, either the players facility cannot provide BGS linked functions - buy sell commodities, black market, bounty/combat bond collection etc. So it's just a personal refuel and repair with a livery section. Or you have to have factions appear with mission board and whatever happens at your station contributes to BGS. If it was me I would make it a vanity item with little BGS interaction as possible so it's not subject to players gaming systems by deploying this bases.
I would also make bases a permanent deployment, not something a player can move on a whim, plus limit them to currently uninhabited planets.
In conclusion I see it as a vanity item for the idle billionaires to creat and tweak and act as a credit sink in the game.