Supreme Commander features three factions with fully robotic armies commanded by pilots (Commanders) on ACUs (Armored Command Units). As stated in the game, those pilots hold Army officer ranks.
Such an army would have few non-officers, and those would probably not play any combat role.
I´ve made some images of officer rank insignia for the three factions of the original SupCom. These ranks are based on the ranks mentioned in the game, from lowest to highest, with some additions to Cybran and Aeon ranks to make them have the same number of officer ranks
. There would be only one rank structure for each faction because a single Commander commands land, naval, and air units.
As for the private and NCO ranks, I´ve still not thought about a rank structure, but it would probably not have many ranks... possibly only Private, Corporal, Sergeant and Sergeat Major (UEF).