I had some further ideas. Which is related to my idea of the SCU character as a persistent reinforcement. Which is that the SCU not be made player controlled. Instead, it must occupy one of the player slots on the map, and well lead a Sorian AI controlled Army.
The SCU would hold the rank of Private and be capable of attacking planets independently. It couldn't lead/create a squad, but, would be able to join a squad created by anyone on the team. Hence, the level 7 or level 8 commander could assign a Sorian AI to attack independently, assist another player on his team, or alternatively to act as a personal vanguard when attacking alone.
The SCU character can't recall and when killed would be deleted from the players inventory. I think this is a possible avenue for adding value to higher ranks.