While guild fortresses aren't finalized, guild wars still appear to be on the development roadmap:
https://ashesofcreation.wiki/Guild_fortresses#Guild_wars
Maybe drama on the high seas could play in as a contributing victory condition? I.e. a victory point is scored is this-or-that number of ships are successfully stalked and sunk by the opposing guild? Maybe an item that could be stolen after a successful channel by a boarder, whom has made it aboard an opposing ship, and is successfully brought back to the pirating/attacking vessel?
Would love to see some guild war elements tie-in with the to-be naval content!