My thing about Veth potentially venturing into polyamory is that I do think everyone involved would be perfectly fine with it and happy to help her experiment, and I think that no matter how they do it, it would not fix her. This isn't to say that she wouldn't get any benefit out of trying! It's just to say that it's not a solution to her actual problem, because I genuinely don't think the problem is that she's lacking any one thing that would make her life complete.
Fundamentally, I think Veth struggles with the idea that there will come a point at which she has to settle. Not in a bad way, just in the sense that she is one person with one life and she will have to live within those bounds. Because the thing is, I don't really think her issue ends at struggling to "have it all"; to an extent she does! She is a good parent, even if her kid is a little rebellious; her marriage is supportive (and has fun sex); she gets to go off to save the world with Yeza's blessing on occasion, when the world needs saving. She doesn't have all of these things all the time, but... that's not really a flaw, that's just a fact of life.
But she started out her adult life settling to an extent—even if she loved Yeza and loved being Luc's mom, she did the safe thing that was expected of her. The goblin attack and everything that transpired after shoved her out of that life, but in retrospect, to an extent it likely feels that that pushed her to find something more that she wouldn't have had otherwise. Being pushed to her limit under the worst conditions made her better, stronger, braver, and at the end of it she found that she could have both her original life and much of her new life—so why wouldn't she then wonder if further experiences of that ilk could do the same?
Crucially, she has not actually run up against a hard limit yet, and as such she hasn't had reason to believe that there is a point at which she has to stop and recognize that there isn't more for her to find. When she was drinking more heavily during missions, even when it caused the death of herself or others, there were no long-term consequences. And the thing is, I'm not saying that she should face that kind of major consequence, but she seems as though she is scared to accept that maybe she could be happy if she stopped before she does.
I'm also not suggesting that she should stop experimenting or trying new things—the Luxon knows I am not one to talk in that realm—but I do think she is searching for novelty not because that would make her happy, but because she doesn't believe that she has the capacity to know what would make her happy. She was unaware that polyamory was even an option, so think of what else she might not be aware of! She doesn't have perfect knowledge of the world, after all, so how can she trust that she's found what she really wants? So yeah, she could fuck someone else, and it might even be an enjoyable experience that she didn't know was missing! But that only prolongs the question of what else she might be missing.
I think that deep down, she's terrified that if she doesn't keep pushing until that external hard limit, she will end up with regrets later, and simultaneously she is resentful that her friends all seem to have reached a point where they are largely content with what they have, because she wants them to have everything. She wants herself to have everything. And she has not yet allowed herself to come to terms with the fact that only she can determine when the everything of what she already has is enough, and anything else is the cherry on top.
