A mode or setting where observers or selected players would enter play as sub-commanders are built, controlling them as you would control a normal commander. Forces could be gifted to a sub-commander or team control shared with them.

The commander might have more control over them, e.g a the player could be swapped with another, or they could be ordered to self-destruct, or less, even perhaps having the option to turn renegade and usurp the commander or even switch teams (team switching might extend to alliances in general, as a setting).

Perhaps a the number of sub-commanders would be capped to the number of waiting players per team.

Forgive me if the idea is not practical, I played some years ago and not that much.