In Chapter 1065 Sanji’s group clashes with a Seraphim unit S-Shark resembling Jinbe as a child which proves to be extremely skilled in Fish-Man Karate just like the original Jinbe. It also appears that Jinbe Seraphim has acquired Senor Pink’s Sui Sui no Mi powers.
I think that the reference to Jinbe Seraphim being still in his child form and yet as big as the original adult Jinbe is actually a foreshadowing for another aspect of the Seraphim. Since we only saw the Mihawk Seraphim compared to Blackbeard and Boa Seraphim separately as well, maybe all of the child forms are as big as their adult forms.
This leads me to believe that Vegapunk was also able to successfully gigantify the Seraphim. They’ll probably grow to be the size of an Oars like Giant. With the Lunarian DNA, Oda has an opportunity to do another callback to Skypiea where we saw the so called Giants with wings, but now with actual Lunarians wings.
Just a theory, but if other than Jinbe all the Seraphim are also big as children it might be that they’ll grow up into actual Giants. It’ll also be a cool way for the Seraphim to represent everything that the science and World Government can put together: Devil Fruits, Cyborgs, Lasers, Gigantification, Cloning. So far they have everything but Gigantification.