I think a good use of beastman currencies would be to trade them for storm/serpent/flame seals at companies. the amount you have to turn in of each is depending on the type (Copper, Iron, Etc).
Also, there should be repeatable quests to build seal count sometime in the future. Unless there are some now and it takes completing all 4 of the first quests to access them, there's no way to constantly increase your seals after those.