[@MelonHead]Doesn't even have to be duels-for-territory, really.  Simply the trappings of the 'verse could be a big help.  Have a team thread with all the arts & farts the team can put together, a showy description of their 'home' arena (since apparently fixed arenas are a big thing here), a roster of their characters, a list of ongoing/important fights, perhaps a description of the team's preferred combat style/ruleset...get some togetherness in one's facepunching.

Whether or not they duel for Official Planetary Control or just because it's the in thing to do, would both be cool for stables of players to work together and build a shared history like that and also be a natural way to funnel newer Arena guys into a support structure to help them get their footing.  Instead of, y'know, one MelonHead doing a ton of educational bouts while everyone else does their own thing.

Dunno.  Heh, I'm a transitory idiot, after all.  But I've seen similar systems do wonders elsewhere.  Might be something to consider if activity's flagging the way I've seen some people mention it is.