A pirate coat can go wrong quickly if the only goal is drama.
The shape matters, but so does the way it carries weight. Long skirts, cuffs, fronts, and pockets all have to move without turning the whole thing into a curtain with sleeves.
For this build, the first work is proportion. How much sweep is enough. How much structure can the front take. Where the cuff stops looking useful and starts looking like theater.
The trick is keeping the romance without losing the workshop sense. It should read as historical wear, but it still needs to behave like clothing.