Interesting idea, but there's too many things wrong with this. There's the technical problem with the hymns that was already mentioned, and a bunch of characters who didn't know that Luke was a replica are being told by Van that he's a replica in this fic.
Asch would never have agreed to be Luke's replacement. If he had, he wouldn't have hated Luke with every fibre of his being for replacing him in the game. Asch didn't think what Van was doing was best; when he heard Van was creating a replica world, the very thing he hated the most, he stopped following him.
Van would never feel guilty about Luke, nor care about him. He was as bad as Asch if not worse for calling Luke worthless and inhuham.

And finally, Van wouldn't think that he's a monster. He believed in his ideals. He believed that it was the only way to save the world from the Score. He felt no guilt for killing everyone on the planet in order to 'save' it from the Score. The only person he considered sparing was Tear, but as he discovered she was going to keep coming after him, he decided that she had to die along with everyone else in order to have his plan succeed.

I don't like this. it's well written, but I don't like what you think as Van's concious. I don't think he ever cared about either Luke, never felt bad about using them. Nor do I think that he wanted Luke to kill him at the end. This is why I love the tales Saga so much, because the bad guys are only bad guys from one perspective.
Why did Dist tell Van about the secret fomicry in Belkend?
If Asch agreed to let Luke replace him why was he so mad at Luke at Yulia City?
The Yulian hymms don't gather Seventh fonons, that's the Sword of Lorelli

Wow...never imagined seeing this side of Van.

Well done.