Originally Posted by Cowoline
Actually, all you need to do is repurpose the discussions from act 3 when it's Halsin related and then have the romances as they are.now run in parallel.

As things go, this is a rather simple change.

I will say that Astarion was a shit choice for it.
That's the point. They can literally make any of the companions poly if they wanted to, all they'd have to do is change romance triggers and have their dialogue when you ask them to share swap from "no" to "yes".

But that doesn't mean that it makes sense. The whole complaint regarding Shadowheart and Astarion in act 3 with Halsin IS that it doesn't make sense for them. By then you spent up to 100 hours of gametime with them, and all their romance conversations hint at a mono relationship with a person that is emotionally damaged and needs your support. That needs to be completely rewritten if their poly, no matter whom else with, were to make sense.

For Astarion, it will never make sense past act 1. It'd require a complete retcon since he opens up in act 2 already, by which point it's over for any idea of poly with him because he needs your support and poly by default tends to require both parties to be confident. For Shadowheart, she'd need to have a sex scene in act 1 already. She's still Sharran by then, so it makes more sense, and wouldn't give off the expectation as much that she's actually a more closed, unsure person, like it does now. They'd also need to change a lot of her dialogue in general, such as her being embarrassed by being attracted to you; that's not the feelings of a confident woman that's open for poly. By the time you reach act 3 and 'converted' her, any poly option should be out of the window, because she's lost all confidence. Sharran Shadowheart, where you kill the Nightsong, would make sense to be open for poly, but again only if you get an early sex scene. Who would want poly without even being together in the first place?