I have seen a good deal of discussions about the Skeleton ship's current workings, and how people don't feel that they are as rewarding and thus don't wanna do them and how the Ships will eventually become threats that will show up on the seas like the Kraken or Megalodon. But this idea i have here is a possible way to keep the Skeleton ship's fort status while at the same time have them show up as sailing threats. Namely, that the Fort ships instead of being a wave of Skeleton Ships are instead taken over by one large Man O' War skeleton ship. This ship could then also have more loot than the normal ships and thus be easier to keep track of compared to the current version of the Skeleton ship battles.
Plus the Man O' War has enough cannons and manpower to function as a sailing fort.