According to the replies, my topic has not been read carefully. Let me give an example.
Skittles, Quido and Altus_Demens are terrorists. Mia is a civilian. Skittles teams up with Quido and they engage a fight with cops. In the meantime, Altus_Demens teams up with Mia and Mia kills Quido. Skittles is willing to revenge by killing Mia, but Mia gets on Altus_Demens' NRG as a passenger, becomes invulnerable, waves her hand to Skitt and gets driven away. Skittles is unable to kill Mia, his enemy, because she abused the anti-teamkilling system: Skittles cannot kill Altus_Demens and stop the bike; Skittles cannot pop the tyres of Altus_Demens' bike because Altus_Demens is Skittles' teammate, Skittles cannot harm Mia because a passenger on an NRG is immortal. I find it unfair. Mia shouldn't be able to become immortal with the help of Altus_Demens, because they belong to different teams. She can still jump on Altus_Demens' bike so Skittles could snipe her; she can try to run away. But she shouldn't be able to use the help of her friend from the other team to become invulnerable.
Please, read the example above and understand what I am talking about... (@Piu)