How about having a new building. Something like a treasure Island which protects a certain percentage of Gold and Grog from all attackers. This Island could be upgraded to protect a higher percentage of your goodies! What does everyone think?
Well its good on defense, but less good when plundering For example I attack way more then I defense, so I would only lose lots of resources on it. For those who doesn't play so much this would of course be useful.
Most of your resources are already protected. When you get raided people can't steal all your gold and grog. So why need this building/island?
I'd see this as a great opportunity for a guild bank. As players put into it(voluntarily or tax) funds can be used to save up for guild perks
