Spawn a native warship (with ballistas, xbows, spaeters, whatever) on the map (F11) outside of the JSHQ dock if the warparty is present there when the player leaves. You can leave via jet, and the natives know you have a jet if the watchtower spotted you.
Actually, native boat random encounters in the north sea would be neat. Random groups of serpents, too. Would keep players on their toes.
