I mean there's an obvious difference between the two factions you've listed is that although we might consider ourselves the rulers of Kusari we are still outlaws and criminals are bound to act more hostile than houses designed to uphold the law. Also it is worth remembering that this is a base within a core territory and houses one of our four stations we currently have in game (not including Battleship or an untaken planet). When it comes to players we have been known to be very lenient in terms of demands and if we attack them or what not. Many of our inRP friends have come about from said interactions in space.
I agree with you that just taxing everything would be rather annoying for everyone involved so I think this approach would have to be done rather carefully and obviously not be too demanding on the owner of the base. To be fair I hadn't considered the use of PoBs for mining purposes, I guess they could be considered a part of the economy but in general these already exist and it isn't required to build your own one for this reason. In fact as a PoB owner I would say building one for this reason so that you can mine and trade on your own would be fairly inefficient when you consider the upkeep and time required to keep it running. But this last bit is just my personal opinion on the matter and holds no real merit.