It would probably be something like,
GK Brotherhood Apoc Formation
1 Grandmaster or Brother Captain
0-1 Brotherhood Champion
up to 10 squads from among the following
1+ Terminator Squads: One squad must carry the Brotherhood Banner. Only one squad in the formation may have a Brotherhood Banner.
0+ Strike Squads
0+ Interceptor Squads
May also take
0-2 Dreadnoughts
0-2 Dreadknights
Bond of Brotherhood: The Brotherhood Banner is both the symbol of the Brotherhood's honor, and a powerful talisman of psychic might. At the start of each turn, nominate one of the following effects for the Banner to give. If the model with the banner is every slain, any effects it gives are immediately lost.
Unyielding Wall: The Brotherhood combines their psychic might into their bodies, allowing them to shrug off even the mightiest of blows. All
GK units from this formation that are within 12" of the banner gain the Feel No Pain special rule till the end of the turn.
Daemonbane: The Brotherhood focuses their hatred of all warpspawn into an aura of holy light that burns all unclean things. All
GK units from this formation within 12" of the banner gain the Holy Aura special rule till the end of this turn. Daemons within 6" of a model with Holy Aura must reroll successful Invuln saves and Psychic tests.
Holy Ward: The Brotherhood chants a litany of purity to thwart even the most powerful enemy sorcery. A
GK units from this formation withing 12" of the banner gain +2 to their Deny the Witch rolls till the end of the turn.
Paladins and Librarians wouldn't be in this formation as they are not part of the normal brotherhoods. Paladins have their own brotherhood and Librarians are part of the command structure.
Edit: because awesome abilities are now free