I think it would spice up the game to have Characters you could find like admirals, scientists, diplomats, traders, etc.  You could find them by exploring a planet and they could function like an achievement.  Provide overall empire bonuses and such. 

Perhaps characters could become available to be found by unlocking achievements.  The more achievements the larger the character pool grows.  This would increase the usefulness of exploring on planets as well as provide a purpose for achievements.  Space ponies could provide a special character.  The character option could be turned off for multiplayer games if neccessary.

This would be fun for the game develpers also as they appear to like to be creative with things like this and with three races it would not be difficult to come up with a short list of characters.  The game developers could even allow players to submit character recommendations to drive continued ethusiasm for the game which could impact future sales of the game and expansions.