I doubt that they would forget what happens to him, even if he dies. [ Estinien just has that kind of effect on others, no matter which side one belongs to. ] However, I do agree that keeping him alive would be far more effective.

[ Kaeya's gaze returns to look at the Regent. ]

Will he become one of us?

[ An Aion for the Kenoma, just like the rest of them, but given that Estinien is one of the Pleroma's most fervent followers, he doubts it would happen so easily. Then again, if the Kenoma is anything like the abyss he is familiar with... maybe he already has a pretty good idea of what's going to happen. ]