I'm much closer the GW1 or GW2 model in thought: Buy the game, play for free, buy the expansion when they are released - sell cosmetics in between. I misspoke about purchasing additional zones. I mean a new galaxy at an expansion level, not individual planets.
Open world online shooter servers are much more expensive to run than regular open world online rpg, because of all the physics calculations. We're going to have to come up with some clever ways to mitigate this for an Indie open world online game that does not charge a sub.