[LordReaver]

PlanetSide didn't fail because of content. PS failed because of no advertising, poor decision making, and then lack of additional content. All other reasons are small time contributors at most.

Probably the best way to make people come back even more, is to further character development. Currently, you gain some XP, your rank goes up, you gain some cert points, but there is no real attachment. There needs to be something that makes characters unique. That is what makes you want to come back and further your toon. Even if it's just cosmetic things. You need the player to have a drive to get to the next thing, whatever it may be. For example, Halo's armor upgrades. They don't do anything, but yet you want to earn them. Or TF2 with hats.

If you go a more functional route, the Vulture was perfect. Anybody flying a Vulture, earned it. They didn't drop cert points for it, they fucking earned it. There is nothing wrong with the tree structure, so long as the earnings are not "better" than the normal stuff, but rather different. Upgrades have been talked about, maybe as you progress, you unlock upgrade slots. That would work also.