Even if I do not participate actively in piracy, I use to help my alliance members/friends to 'freeze' any colony of enemy with a pirate fortress in it. A raid sent from the lvl 30 Fortress to another side of world - for quite a long time enemy won't be able to cancel the colony to use it somewhere else.
An option to build something else - nothing against it, would be nice to be able to have 2x ports and 1x shipyard in the town as we don't have other sea buildings currently.