Alright, I think I’ve gotten a grasp on his character (though it took 6000 words) so I have an idea for a oneshot:
Alucard admired Gusion for many things, but his god awful posture was not one of them
Aka: Headcanon where Gusion missed out on a lot of tips about swordplay since he never learnt it as a child, and Alucard is determined to teach him all of it.