I don't have much time for a co-op just yet but I'm willing to dish in a few ideas on this forum. This look like a scifi space thriller like the above said, but I can feel a touch of steam punk in it, which is always a cool but sometimes not really used theme. Your story looks like it could be one of those centering around a lot of characters who's actions effect each other in the long run, like Baccano or Durararara!
Although maybe not with pirates, this cast looks like on where most of the important characters would be crew mates to something big, maybe a ship, or a shipping delivery organization... A fun collection of people under one roof, like Kekkai Sensen or Bungo Stray Dogs. I'm sorry, these are all Japanese. I have no life, I know.
Any one of them could be the bad guy. Maybe the bad guy doesn't have to be bad, maybe your comic could be that one interesting one where conflict is really just a conflict of interest for what is best, not evil and justice!
I don't know what the setting would be. Alternate universe? Maybe the far future, so there's technology but maybe a pollution screw up kind of made the world more primitive at the same time. Stand Still Stay Silent is a we omit that follows that theme awesomely.
Hope this helped a little bit! As for a central conflict that literally narrates where characters will go and why and what they will do, I it usually comes to you when you continue your comic and read widely!