Im affraid Wyll cant be Hexblade, since (unless i read something wrong) Mizora would have to be his Blade ...
Fiend Warlock + Pact of the Blade tho, that would fit him perfectly.
Well, would be ok too, I guess. I want him to be more versatile with the rapier, since it seems to be Wylls signature weapon. I guess a higher Dex would help with the worst.