Mentioning "Tribes" gives me hope for this game. Tribes' strong point was that a player could jump onto a team and be instantly useful. Whether it was setting up defenses or even hopping on Offense and capping a flag you could do it with absolutely no team-affiliation or co-ordination.

Things got magical once you DID start to cooperate with a group of teammates but it was still FUN to just jump in and adopt whatever role was needed.

It's something that's missing in PvP in MMOs currently. The roles in high-end RvR are so Gear/Trait driven that it becomes difficult to just "jump into the fray" and be anything other than damage-sponges for Guild groups.