UFO: Enemy Unknown had superb system:
Commander XCom1 rank6 Commander.GIF Only one allowed over all X-COM Bases, requires at least 30 soldiers in all bases.
Colonel XCom1 rank5 Colonel.GIF Most experienced Captain is promoted to Colonel if opening present. 1 Colonel for 23 soldiers, limit of 10.
Captain XCom1 rank4 Captain.GIF Most experienced Sergeant is promoted to Captain if opening present. 1 Captain for 11 soldiers, limit of 22.
Sergeant XCom1 rank3 Sergeant.GIF Most experienced Squaddie is promoted to Sergeant if opening present. 1 Sergeant for 5 soldiers, limit of 50.
Squaddie XCom1 rank2 Squaddie.GIF Perform any action that qualifies towards promotion, may not be given with high troop counts.
Rookie XCom1 rank1 Rookie.GIF Starting rank for all new recruits.
Can anyone help me to understand UFO AI ranking system?
It seems to me Ill soon have all colonels in the bases