Well in regards to claiming a star system or having a fleet or defence for the area, this could be done through brute force. Depending on how much an area can be impacted, theres nothing stopping you and a group of people simple killing everyone in a particular system and telling people to stay out, along with having other players acquiring a fleet of various ships to help with defending your "claimed" location.
This will become easier once the Wings section has been added to the game, but it remains to be seen how much we can affect or change a particular area. Although we can't destroy stations, I do wonder how the mechanics of the game will behave, if you had a group of people go in and kill off all security and stop people from coming and going from the station, although there is no way currently to take over a station and change its faction/owner.
The only real benefit I can see to doing all this at the moment, apart from being just for fun, would be to corner off a mining location, or a station with a particular commodity in order to keep it for yourself.
Although we will most likely never see an ability to build your own stations/outposts, it wouldn't take too much to implement the behaviour mechanics in allowing groups to be able to "own a station" in a way that just means the station would not fire on those that have taken over. This could then be further expanded on, by either having missions open up in order to reclaim the station for a specific faction, or take over the station yourself. Theres many many ways you could allow events to unfold and be acted upon and add in many variations of gameplay, without having to introduce new assets or large game changing modifications to the current engine.
I do look forward to what FD are going to introduce with and after launch, as with this game engine as it is right now, there are a lot of ways to introduce new gameplay mechanics and create a "living" galaxy and story.