[Discussion] One Piece replacement of capture

Hi everyone.
I'm starting gathering stuff and ideas to create a One Piece based game using Essentials. What I'm thinking about at the moment are possible alternatives to the regular Pokemon capture.
I don't like too much the idea of throwing balls at pirates or marines to capture them!
What I'd like to achieve is something that lets you add characters to your team based on the One Piece world.

For now my ideas are:

• something that simlulates the fact that you convinced your opponent to join your crew.
  This shouldn't be too different from the official Pokemon games cause you'd have to weaken the opponent and then try to convince them, but I don't know exactly how to make it work yet.
• something based on wanted posters, by collecting them (by defeating "wild" fighters or found in special places in the world) you make the character join your crew.
  The downside with this idea is that it isn't so accurate for marines as they shouldn't have wanted posters, and a lot of items must be created to let the player recruit everyone.

As you may have understood, the whole point of this thread is to ask for other ideas on how to replace pokeballs for a One Piece world. Feel free to propose different approaches or refinements to what I've said.
I'll show something regarding the project very soon.

Thank you in advance.

I figured out that using side quests may be the better way to go. One Piece characters are unique and most of them have a story to tell, so that's perfect.