I suspect sponsoring pirates that raid other nations' ships (and probably coastal villages as well, as that was common in real life) will cause problems with both Vathcras and Oxfreight, maybe even Terus or Drastonia if the pirates go that far. With your navy probably only able to hold off at best one angry country, having fleets of pirates pillage everybody will probably lead to Ryuku's island being blockaded and starved out.

It's probably a better idea to have the pirates only attack your enemies, not neutral parties.