In a post by Malfador Machinations (probably the programmer himself, Aaron Hall) a long time ago, they said that they had originally planned for each ship to have its own captain and for the captains to gain experience and possibly have special abilities. Apparently it was too difficult to do at that time. So, crews gain experience but there are no individual "heros" in this Version of Space Empires. But, there will most likely be a Space Empires V eventually, and we can request heros for that one.
