How did the Rüstsatz system work?

[Broncazonk]

We all know about the Rüstsätze kits, the prepackaged field modification kits that usually came direct from the aircraft manufacturer. But how did the system work?

1) Was there a catalog to choose and order from? (And did the cost of the kits come out of the unit's budget?)

2) Who had the authority to order them? Staffelkapitan? Gruppenkommandeur? Geschwaderkommodore?

3) Also, on a related question, who had the authority to delete the outboard 20mm wing cannon (and later 30mm) on the Fw-190? I've read that certain Experten had the outboard weaponry deleted off their aircraft for reasons of weight and safety. (I've seen the safety part--repeatedly--in gun camera film. Hits to the outer wing of a cannon-armed Fw-190 would often detonate the cannon ammunition box, being armored or not, and the wing separates dramatically at that location. Example of this, the .42 -.48 second mark in this gun camera film: https://www.youtube.com/watch?v=tHKj3CZK3WY

Bronc