The only time Astarion sort of offers "his gift" himself is when the player starts reading "morality" and chooses to branch the dialog through swearing. Morality - and what did you learn? Scolding - what was I supposed to learn? Provocation - how to love me? Scolding - and what makes you think I haven't learned? So it's over? The only option for reconciliation - No, we'll work it out. Then the poor guy grabs his heart with trembling hands and says, "you're the one I love, the one I want to be with". It is not good. The other 3 options are pretty bad. 1. I want to be a vampire. The player doesn't know, Astarion doesn't know, in fact, only Mephistopheles probably knows what an Ascended Vampire is. Can he turn others? And into what? Tav didn't know what a spawn was, and Astarion told her about it, and this is a new level. It's illogical to ask him to do that. He should offer it himself. 2. I want your body. Tav is an emotionless creature. Listening to his partner with his ears closed. That's throwing all morals out to the bear in the brothel. 4. I'm not your pet. He called Tav that before. Cheeky little puppy. Bag of blood. Baal's little baby (for TC). He likes to give names. And here it's a grudge. TC has a unique retort after turning to the spavn (if you got the assassin guise) that I was an unknowable critter anyway, then the spavn status doesn't confuse me. To which Astarion says I knew you'd be cool about it. Such a Tav-TS didn't take offense to the pet.
We are not asking to change Astarion, we need to give Tav a chance to respond positively. Astarion will also continue to bend the branch of dialog about the turn.