Command Squads may only be taken for Captains (one command squad for each Captain).
There is no 'Sergeant' option - because they're all veterans anyway, a Sergeant would have no different stats, only options.
The Company Champion is an optional extra - the basic squad is 4 vets and 1 Apothecary. All have chainsword and either bolters or pistols.
They can have bikes.
Any can replace pistol or sword with:
Storm Bolter,
Flamer, Plasma gun, Meltagun,
Combi-whatever,
power sword or fist,
lightning claw,
thunder hammer.
Pistol can be replaced with Plasma Pistol.
Melta bombs and Storm Shields can be taken by anyone.
Right then - Librarians.
9 powers:
Avenger - essentially an AP3 heavy flamer,
Force Dome - 5+ invulnerable for Librarian and squad until end of next player turn,
Gate of Infinity - Librarian and squad Deep Strike back within 24", but with minor risk...,
Machine Curse - shooting attack causing Glancing Hit on 1 vehicle within 24",
Might of the Ancients - Librarian gains strength 6 and rolls 2d6 armour penetration.
Null Zone - all enemy units within 24" re-roll successul invulnerable saves for rest of player turn ,
Smite - 12" range, assault 4 St4 AP2,
Quickening - gains Fleet and Ini.10,
Vortex of Doom - 12" St10 AP1 Heavy1 Blast...failed test = blast centred on Librarian without scatter..