The third alien ship could maybe be like a drone-carrier, instead of weapons it unlocks more bays for mini-drones that attack enemies, the different weapon slots unlock different weapon types on the drones? Quote hral
3 human and 2 aliens, would be nice with 3 of each :)maybe an alien flyer, so alien can also play space missions.
One skill it could have would be turning its self into like a hive, stationary with drones buzzing around it, to deny passage.
A second could be the drones all switch to healing near by units - but is a heavy energy drain.