Still holding to my theory that Garling has eaten the Cerberus fruit.
The Cerberus guarded the entrance to the Underworld in Greek mythology, perfect for the captain of the Holy Knights who guards the Holy Land (actually Hell)
Imagine a giant 3 headed dog, each one with Garling’s hairstyle and face. A different head speaks everytime Garling talks and they each have a different aspect of his personality. And Garling could be an awakened mythical Zoan like the Gorosei are, which means he could still be a Haki man but just with a mythical Zoan like Crydo.
It would just be perfect. Do it Oda.