Parents and Detachments work just as they do now.
Auxiliaries
Crossbowmen, Handgunners, Archers, and Free Company may choose to deploy as Auxiliaries instead of as Independent units. They must be initially deployed within 3" of any Parent or any Independent State Troops unit.
- They don't cause Panic
- They may Support Fire for any parent or independent unit within 6", as long as they have LoS
- They do not use parent's leadership, cannot Countercharge or Support Charge
- They can purchase unit upgrades and are not limited to detachment sizes
The bonus seems minimal, but it's a way to emphasize the rigorous training of these troops. Not all supporting assets need to be tied down to any particular unit from the start, they should be deployable anywhere they're necessary. Gives the Empire player a bit more tactical flexibility in a little-used (or perhaps just overlooked) aspect of the army.
Drills
These are specific orders issued by the unit leader (requires unit champion, if a detachment then it requires parent unit to have a champion or a character). Militia cannot perform these drills. Requires Leadership test to succeed and can be cancelled at any time. Lasts one turn and each unit is limited to one drill per turn.
Marching Orders - Make all Enemy Sighted! rolls for that turn at +1 Leadership.
Hold! Hold!... FIRE! - Stand and Shoot is resolved at short range.
Shields up! - Requires shields in the majority of models in the unit. Reduce unit's Weapon Skill by 1 and raise Armour Save by 1. Unit cannot Charge or March this turn.