Either way it would be considerable change, which would likely be picked by only a few players.
And yeah, I know it would only be one line, but there are some bigger implications about the follow up lines and scenes.
What would the considerable change be? What would the bigger implications be? No seriously, tell us, because so far you have not offered anything but vague statements.
I know writing fiction is hard, but as someone who gets paid to do it, I can say that the requested 'I just want to be with you' line specifically would go a long way to hammer home how bad the situation actually is. Do you know why? Because the player would have just given Astarion the perfect thing to use against them to get them to agree to be his spawn. He would offer to turn the player like he normally does, and if you so much as hesitate he can slap you in the face with 'but you just said you want to be with me', and now you're stuck in a situation where you either own up to wanting to be with him and let him turn you, or he breaks up with you and gets to call you a liar because clearly you didn't mean it if you don't want to be his spawn. So I don't see what the problem with this change is to you, since it keeps the abuse narrative going in a very effective way. It's actually
more effective than anything we have right now, soo... yeah.
If we had an 'I don't want anything from you' line, Astarion could just go 'that's cute, but how about I make you immortal?', and the dialogue would be basically the same it's now. Lot less changes here, but it's also less effective at shining light to how toxic the whole thing is. Still a good neutral option to have, though.
As for the ability to stay with him and not be turned to a spawn (which is not mentioned in the original post and is not something I'd personally care for because I do think that Astarion's ultimatum is important to his character consistency since he's still, you know,
Astarion), that's already in the game, you just have to go through specific hoops to get it. Implementing it to the dialogue discussed here would be a big change and the main reason I think this will always remain an fun 'what if' thing, but it's easy to keep the theme of abuse going with this as well by giving the player maybe one or two long rests to come to a decision, and then force it upon them. If you make it to the end game without giving him an answer, then you make the decision in the last dialogue. But like I said, this is a change I don't think would ever be implemented since it would require a lot more work and while it would be nice, the ultimatum is there for a reason, but in the theoretical world where this did happen it still wouldn't change the core theme of the ascension path, as you'd still have to give him the yes or no answer which leads to you either becoming his spawn or breaking up with him.
And as for changes to the other characters, yes they need more content, but we're not discussing that here. We're discussing Astarion. Let's stay on topic and not drag issues not related to the matter at hand into this to try to redirect or distract the conversation. There are posts discussing the other characters already all over the internet, and you can always add to those posts if you want.
