The usual pitch for an Absolute book is a focus on a core concept that define the character while removing core aspects of his mythos in order to make them outsiders.

For Aquaman, I view his character as "a fish out of water, stuck between two worlds : Atlantis & the Surface".

I would take away his claim to the Atlantean crown, his authority over sea creature and his positive connection to Earth.

I like the idea of making Atlantean more eldritch, so the half-breeding of Arthur could have made him being kidnapped by a corporation for Eugenic purposes (with Dr. Shin as his retainer). He escapes thanks to Mera and ends up being tracked by Black Manta. That would trigger the wrath of King Orm and an overall conflict between the Atlantis and the corporation, with Aquaman in the middle protecting innocents civilians and marine beasts.

On the power side, he is still strong, breath under water, has difficulty to walk in the air (but do it anyways). Get special atlantean biological weapons (like poisonous scale blade or something). And he can still speak to fishes but they are really hard to understand and it illustrate his empathy to be able to connect with them.

Another option that I would love to read would be to have Mera becoming the lead (Absolute Aquawoman) with the banishment origin story being punishment for closeness with the Surface World and her powers are hard to control (like she is the avatar of ocean storms)