donīt think more races will add anything to the game, apart from giving a even bigger headache to balance the stats.
more reasons to attack is what i would go for...
like giving good xp for killing structures
or giving xp for killing ships
placing a virus in the system of the planetary defence (fleets cant be launched for x ticks)
stealing ressources
stealing ships with good value gains
sabotage asteroid mining (roids only give 50% income for x ticks)
destroying asteroids
in addition defending fleets or attacking ones turn sides last minute (if ordered ofc)
etc etc...
expecting something like that is like waiting to win the lottery though