the cooldown could be longer indeed to prevent exhaustion. else i still think that nations with a large population and many, many ports should simply be ready to get attacked or threatened quite often at various places. it´s kind of realistic in overstretched empires and gives a little more balance. making hostiltiy cost doubloons or else is for sure the worst idea. the weaker economies will be choked even more than now. i´d wish to have an idea for the hostility itself. flipping in a single action, without the attacked nation being able to react isn´t that good. maybe it could happen in 2-3 steps. one step per day. so a nation knows there is going to happen some attack and can reinforce that particular area. good pvp-action might develope there.