This is why I find the current dialogue options problematic and why I would like to see more choice.
(...)
'So, tell me what you desire. What can I do for my dearest pet?
I want to be a vampire, like you. (selfish, transactional)
I want you, I want your body. (selfish, transactional and completely insensitive!)
You can tell me that you've learned something from all this. (Preaching and hostile)
I am not your pet. (hostile)
These options are far too similar. There is no altruistic or reassuring option and I really feel there should be.
Personally, I feel that option two is the most problematic here, because Tav knows Astarion's past. They know how he was used by Cazador and the effect that had on him, so it seems very odd at this point in their relationship for Tav to say they also want to use Astarion.
(...)
I agree with OP and the others.
My humble suggestion would be to add 1 positive/good answer for tav/the player, which will lead to the same existing voice line of Astarion, which he is giving to Tav's answer "I want you. I want your body": "You've earned it. But don't you want more - don't you want eternity? One more bite is all it would take. That's what you want, isn't it? To be mine? Forever?"
No new recordings of Neil would then be needed. So instead of the selfish, transactional and for most romance players OOC answer "I want you. I want your body", add one of this:
"I'd like to be by your side, that's enough for me."
"I want to be/stay with you."
Or something similiar in proper english, which fits to Astarion's existing voice line I mentioned above, but which would be a more positive, sensitive, altruistic answer. Simple.
'I just want to be with you my love'.
Simple
+1
That would be perfect!