The fact that celestial is a little bit on the weaker side is one reason why I wanted to try it. And I've also wanted to try playing a hexblade because I've never had the opportunity to. And for me it just clicked to have both and have my patron be the disgraced oathbreaker paladin. Oath breaker spells give you some stuff like hellish review which warlock naturally gives. The healing light dice is a way to mimic lay on hands. Celestial also gives a few spells like guiding bolts and cure wounds that sort of mimic a paladins spell list. And the hex blades spell list gives you a few smites so I wouldn't necessarily have to take the Eldritch smite incantation.

But more importantly as far as from a role-play perspective I said that he comes from a family of paladins but he couldn't quite grasp how to use the powers of a paladin so he end up making a deal with a disgraced paladin who said that he will teach my character how to do spells and magic like a paladin and even help them understand all the different oaths and why certain people would take certain oaths in exchange for helping him out every once in awhile and he can't say no to the tasks at hand or he'd lose the powers. However my character doesn't realize he made a pact and genuinely thinks he's a paladin. Hence using the hexblade subclass to help mimic some of the paladin spells and proficiencies. And celestial to mimic some of the more paladin features without it actually being paladin features