Having finally seen Aquaman, Namor is def doable.

Aquaman has certainly cornered the market on the bio-luminescent vision of Atlantis and affable nice-guys.

In addition to being proud, arrogant and honorable, Namor is also a savage. He's not ambivalent. Marvel will have no trouble differentiating Namor from Author.

WB/DC may have to give the current Aquaman of the comics a dye-job and longer locks to reconcile the two iterations now that Aquaman of the movies is a thing though.