Consider 8-person PS Party When Joining A Warzone
When in a large party, it invites everyone to the warzone. It looks like the game tries to balance the server rather than splitting onto different sides... what this means usually is that the game cannot start. So either don't auto-invite your party to a new warzone or (better) allow a party to split. :)
16 player Party is now possible..
Just tell your friends to join later and when enemy team has more people you can kick noobs out from your team so your friends can join.