Elder
The Elders form the Brotherhood's ruling council. Individual Elders are occasionally leaders of localized splinter chapters of the Brotherhood. Under normal circumstances, the ability to become an elder is reserved for Paladins, although there are exceptions, such as Elder Elijah, who was a scribe.
Elder clothing:
Commanding officer
The Commanding officer is the leader when the elder is not there, The primary goal of the commanding officer is to keep a eye on the generals. If they are not doing there job right in battle a commanding officer can take the command.
They are simply an example for the military to keep the morale high.
Commanding officer clothing:
(I now this is the elder robe from new vegas but it's now the general and commanding officer robe it will come to fallout 3 with a mod the Elder Lyons' robe is already in the cheating chest of new vegas but new vegas got a mod that makes fallout 3 work together with it)
General
Generals control all of the Brotherhood's military. They report to the Elder when required. They obtain the title of General by showing outstanding performance in military tactics and combat. They help decide the titles of the most promising recruits from Initiates and Squires all the way up to the Paladin Lord and Knight commander.
They wear the same clothes as the commanding officer
Paladin Lord
Paladin Lords are paladins which lead special operations outside of the army. They only report to the Elder and commanding officer. Their operations are sometimes kept secret from the Generals, because they can go against brotherhood military regulations. They are given specially selected squads that will follow the Paladin Lords without question and are forbidden to talk about their missions to other members of the Brotherhood.
They wear T-45d or a T-51b power armor normally without a helmet but it's about what the player like.
Paladin Commander
Paladin Commanders control squads of paladins and group together in the A ring to discuss battle plans, they also report directly to the general.
They wear T-45d or a T-51b power armor normally without a helmet but it's about what the player like.
Knight Commander
Knight Commanders control groups of knights in the brotherhood and group up inside the A ring to discuss battle plans and such at a round table area. They report to the general.
They wear T-45d or a T-51b power armor normally without a helmet but it's about what the player like.