I haven't looked into any vessel-knight theories but I can see how it would be like . thematically pretty cool.

mainly, it's the similarities to Kris. like, you've created a copy of them maybe for maximum soul compatibility. the aura farming, poses, wielding a sword. it's interesting. furthermore, if it really is "your" form, the red damage numbers contra red soul ... well it kinda lines up.

but I do think Rudy or Asriel are more likely to be the knight. I still remain opposed to dessknight but I wouldn't be surprised, I just think it’s not as complicated as some theorists make it out to be, like how the soul actually belongs to her. it could just as well belong to no one, an apparition for you and you alone

I guess we'll find out soon