I guess, this topic has been discussed. I propose to add to the game collection. For example, when a player makes an action as a fight, outbreaks, killing a boss or help other players - he drop items (part of collection). When the player collects all 5 pieces collection - he gets a bonus. Bonus - money, experience, energy , stamina. As an option bonus - is the subject of inventory.
I like anything that makes people actually play for a purpose. The more they play, the more familiar with the game they get. The more objectives that they have to complete that are not either gimmies or take extended amounts of time, the better. 10 from me.
Sounds like a good idea for the bosses. There are already sets of mateys, ships, & weapons to be collected at various levels when battling.
At the time there was very little community interest around this (one vote from you) so we decided not to move forward. As with your other idea, the more votes the better.