Well people answered for me.
The player VIP is selected by vote at the beginning.
That's why an NPC like a little boss as the VIP can be an other idea (to be sure, teams have the same VIP to protect, like a jedi master and sith lord, etc...)
Ah and, i was suggesting that, both team can have the VIP at the same time, or like Voidstar, first team has to protect the VIP, then the other team for the second round. (it can be like Voidstar too, like "checkpoints" to reach with the VIP !)
EDIT : And an other thing to balance the VIP, if you want a player VIP, he can have a "VIP BUFF" that makes him taller with mini boss stats (same for each team, like same def/hps or you can also put different bosses stats, like a DPS VIP with lot of health and huge damages, or a Tank VIP with medium damages and huge HP pool and defenses, etc...).
Or maybe just a VIP with a little bit more stats than others, but with specials abilities to protect himself.
Etc.. ^^