We know when we deploy pirates they are not coming home--whether they are still alive at the end or not. What we DON'T know is what happens to them after their victory. We know that the attacked island quickly rebuilds so maybe the "conquering" pirates simply get absorbed into the new culture. However, what if there were a way for the defending island to...convince, cajole or otherwise capture some of those pirates? Allow me to present: Turncoat Tavern Using sophisticated methods (lots of grog), the Turncoat Tavern can keep a couple of the surviving attacking pirates and allow them to be deployed in future battles. As the building levels up, a greater number of pirates could be kept. This could work in a couple different ways. 1. Maybe the system is random. It randomly chooses from the surviving pirates. 2. Or maybe the player can actually choose which pirates they would like to try and keep. Lvl1 building could only hold 1 type of pirate, Lvl 2 could hold 2. What happens if you set the building to get Heavy Gunners but no Heavy Gunners survive? Then you get no pirates! Try again! Deploying the pirates would be similar to the guild ship--OR it could be limited in that if you have more than one type of pirate you can't cycle through them (you just use them as they come out). But wait Midoki--I hear you grumbling about all the extra time and code. To sweeten the deal for you, the Turncoat Tavern as a cooldown timer (maybe 1 day) that can be reset by gems! We know you love them gems. This would be a fun mechanic that no other game has (I don't think). It would also give attackers an incentive to be more strategic with their troops because if they end up with a lot of surviving troops at the end they are potentially giving the defending island an advantage in a Revenge fight.
Until you're stuck with an army full of lv1 buccs some knucklehead dropped off his GS with one second left to fill your tavern, and then have to dump them in a forfeited battle to toss them away and make up fresh space for actually useful pirates - further passing them on.