One of the things the reason why I created Twst Elsa was to be that person who Vil can really trust enough to show his imperfect side with with no judgement. Sure he has Rook, and Rook is ok with Vil's imperfect side but as I see probably, I think Vil never really show any weakness in front of Rook nor anyone, even when he apologizes for what he's done, he still act professional. So having a friend who he can be himself the most with is something different to see. I think?
Sure, that and, having an external party that can offer a new perspective on matters is always good, so the idea of a character like your Twst Elsa can work great.
But, if you want to like, work with canon only, and from my point of view, it is not necessary. That doesn't mean you can't do it, of course! Having a new friend that Vil clicks with and can trust deeply in consequence would probably help accelerate his process of healing a little. But what I'm getting to here is, if this also like, about the matter of the asks that mentioned giving Idia a Twst Persephone to help him get there, this is why say it's not necessary. Vil essentially needs to learn to be more lax with himself and that he can place his trust on the others to help and listen to him. He can learn this beside the friends he already has, like Rook and Epel. Vil can learn to trust Rook truly, talk to him honestly, and set his boundaries when Rook is putting things too bluntly for him. He can learn to listen to Epel a little more closely, while Epel does the same so they can reach certain agreements or be in peace with their disagreements. Vil, much like Idia, doesn't need a romantic love interest to sweep him off his feet and "save him".
~Mod Lag