I thought that that might be the idea you were considering. Including units that would have defected to Successor States, been disbanded or who survived Terra but whose fate is otherwise unknown:
Divisions
11th Royal BattleMech, 26th Royal BattleMech, 39th Royal BattleMech, 135th Royal BattleMech, 146th Royal BattleMech, 150th Royal BattleMech, 299th Royal BattleMech, 309th Royal BattleMech, 316th Royal BattleMech, 328th Royal BattleMech, 331st Royal BattleMech, 341st Royal BattleMech, 349th Royal BattleMech
1st Royal Mechanized Infantry, 13th Royal Mechanized Infantry, 17th Royal Mechanized Infantry, 27th Royal Mechanized Infantry, 31st Royal Mechanized Infantry, 34th Royal Mechanized Infantry, 50th Royal Mechanized Infantry, 65th Royal Mechanized Infantry, 120th Royal Mechanized Infantry, 131st Royal Mechanized Infantry, 132nd Royal Mechanized Infantry, 157th Royal Mechanized Infantry, 159th Royal Mechanized Infantry, 169th Royal Mechanized Infantry, 183rd Royal Mechanized Infantry, 226th Royal Mechanized Infantry, 242nd Royal Mechanized Infantry, 279th Royal Mechanized Infantry
61st Royal Jump Infantry, 80th Royal Jump Infantry, 106th Royal Jump Infantry
13th Royal Infantry, 44th Royal Infantry, 50th Royal Infantry
Regiments
11th Royal Heavy Assault
135th Royal Striker, 741st Royal Strikers
29th Royal Dragoons, 121st Royal Dragoons, 367th Royal Dragoons, 405th Royal Dragoons
902nd Royal Hussars
43rd Royal Light Horse, 55th Royal Light Horse, 59th Royal Light Horse, 90th Royal Light Horse
22nd Royal CAAN Marine, 31st Royal CAAN Marines, 35th Royal CAAN
82nd Royal Jump Infantry
13th Royal French Demi-Brigade
125th Royal Hover Armor
587th Royal Artillery
188th Royal Independent Aero Wing