Treasure Fleet Ochalean Privateers ("Wharf Rats") Rogue faction
by Marc SaindonBy 1007 AC, the Ochalean crown decided to remain neutral in the War of Wrath, to avoid being swept in the conflict between Alphatia and Thyatis, and declared its independence. With Thyatis winning that conflict and Alphatia falling (alternatively, falling into a civil war after Eriadna's death instead of sinking), the Empire will want its wayward province back, and has the galleys to get it back. Ochalea in the almanachs has no navy.
To counter the Thyatian threat and lacking the time and manpower to build and train an entire fleet, the quickest solution is to resort to privateering (think of England's Sea Dogs against the Spanish Armada). Naturally, this isn't "piracy", as privateers operate within the bounds of Ochalean law and with a permit (letter of marque), but it's piracy to those raided. Ship-wise, a lot of the early embarcations are Ochalean merchant ships (junks) converted to military purpose.
Encouraging privateering might contradict Ochalean principles of peace, but having someone else do your fighting instead of you (and providing plausible denial) is a way to stretch these principles.
Ochalean privateers are a mixed lot. Many of them aren't even Ochaleans, as the letters of marque can be obtained by any captain, so expect Nuari warriors, Minrothad corsairs, Ierendi sailors and even Yasuko pirates (Mystara's "Jungle Japan") to join in the crews. Some are privateers in name only and indulge in piracy on all banners for some quick loots, others aspire to eventually create a professional navy for Ochalea.
While 5e doesn't have an official "Pirate" Rogue Archetype, you could use the Swashbuckler for game mechanics. The ship and its crew serve as the Rogue's equivalent of a Thieves' Guild. Also, not everyone on board allied as crew mates will be Rogues: some are just non-fighting Commoners working as sailors, some are straight-forward Fighters, and an odd one might be a Bard or Sorcerer.
Adventures might involve raids on the Isle of Dawn, sabotaging Thyatian galleys, exploring weird islands (and maybe claim the Isle of Dread for Ochalea), repelling Alphatians (Zandorians and otherwise), battling rival crews, gaining vengeance on a white whale, and exploring. The last one calls out to historical China's brief shift away from isolationism during the Ming dynasty, when it sent Zheng He exploring lands as distant as East Africa. With the privateer fleet active, Ochalea is meeting new people, opening new markets, and getting new resources. Possibly in the works is an extension of the Pearl Island-Ochalea defensive alliance to countries such as Minrothad (who needs friends anyway, and wants one big island from Thyatis).
The choice of the Rat as a symbol is both for its connotation as a pest (and meant as an insult by more "civilized" people) and how its paradoxically recuperated as a badge of merit, as a symbol of resourcefulness and resilience (a bit like some early insults against the LGBT and Afro-American communities have been turned 180 degrees by members of these groups, or even like how Yankee Doodle was initially used by the metropolitan British to insult the Colonials).
(image from: https://www.deviantart.com/retrostyle-games/art/Female-Pirate-Concept-Art-Realistic-900831116)