Although many MMORPGS shoot this idea down right away because of the many problems it produces, I think HJ should try it out in testing or in beta.  I can't really say much for how you can fix its stability in-game, but I can atleast put forward an idea for gameplay purposes.

As an example, in some mmorpgs, when a leader invites a member to the party, he give that certain person -Tags-.  Diffrent -Tags- do diffrent things, such as allowing the member to invite others, trade, chat, and even kick people out of the team.  So naturally, this way the leader has alot of options with what he can do with his team.  In addition to these -Tags-, you could just add a Voice Chat permission.  That way, only the leader and who he wants to can speak.  No more senseless chatter lagging the crap out of people.  This could be adapted for a even bigger scale like raids and PVP events.  I even recall reading a artical awhile back about Voice Communication with NPCs, which I must admit, sounds damn cool.

I just hope you guys don't over look such a usefull tool just because other mmorpgs couldn't pull it off!