Well, you can let Volo put an ice pick in your eye, you can let Araj turn your blood explosive, etc. If someone wants to be a vampire spawn because they're convinced they'll be able to talk Astarion into turning them into a full vamp later, or just didn't think this through because powah, they should be able to do it.
It could also be an option for a Durge who
loses a duel with Orin. Or non repentant Durge who chooses to destroy the brain. Make some dice rolls in the ending, maybe at least keep your sanity if Astarion's control wins over Bhaal's.
