Having run it several times, my most disliked part of the MSQ is:

[Iscah]

Pretty sure that Laurentius had plenty of "second chances" prior to being recruited by the Crystal Braves, according to Buscarron(mentioned after your first run in with him). I do remember him feeling guilty during Baelsar's Wall though. I think he was just easily manipulated though for the most part.

That's exactly the thing. He was given a second chance and he was trying to take it when we came to him with what seemed like a fantastic opportunity for him to do something good with his life.

He is easily manipulated and that's why it was such a terrible thing for him to end up in a group of people eager to manipulate him – apparently by preying on that intent he had to to do better, and telling him it was the right thing to do in the grand scheme of things.

Laurentius was always a weird character to me, it feels like there was supposed to be way more to him after Baelsar's Wall but then he's just never brought up again.
Maybe in the future he'll get some small part in a role quest or something.

We don't see him again after Baelsar's Wall, but we do hear that he and Yuyuhase are apprehended, and Raubahn asks our opinion on whether they deserve death or mercy. From memory that was still only as a precursor to them getting a proper trial, though, so as far as we're aware they might still be awaiting sentence. It's a plot thread they could pick up when they want to.