That's an awful lot of complexity to throw into an archetype. Couldn't you just add a Hex ability, recharging on a short rest, and maybe the shadow pet? I don't see the benefit of adding spell slots to this equation.
The goal is to replace the Warlock Patron, instead making it a Fighter archetype.
One interesting way to help fill up the class features would be to allow the Hexblade to select from either Wave, Whelm, or Blackrazor (or something thematically similar and fluffed otherwise) as their patron, much like how a Totem Warrior Barbarian might choose a personal totem. Then their subsequent archetype abilities could be colored by this choice.
I had planned to let them choose Warlock Patrons (Fiend, archfey, etc.), and have the abilities colored by that. Basically the same idea.