Exactly, which is really cool and I'm doing the same - I intend on merging the sea guard with the corsairs under the command of a fleetmaster and sea helm for a start, also with blues and maybe silver for weapons. It suits them well as the guard is more defensive while corsairs are made for assaults - after all, long spears, long armor and tower shields don't suit close combat in confined quarters at all - it's a place for short armor, cutlasses, axes, daggers and crossbows, especially on a ship's deck, although there are some exceptions like the Spanish, who used to take their tercios on board for protection and that worked.
Anyway, do you plan to add a fleetmaster to your fleet?