Not gonna lie, I’ve been discussing doing just this with my players. Helps that one of them lives there. Make the players fishermen, throw in the legend of the Isle of Demons, set it in the 1930s and you’ve got a great little campaign!

So not so much different as just increasing in complexity of actions to defeat the boss.

You could check out Voidheart Symphony. The Minion-> Enforcer -> Vassal enemy progression increases the complexity of actions required to defeat them (with the Vassal requiring a number of rp related actions to even attempt, and gains additional abilities if its Enforcers are not dealt with first)