1. Try posting a purely Gunner question in the Gunner forum - most ARRSErs won't have a clue what you just asked.
2. Too many exclamation/question marks = sick mind !!!!?!?!?!?!?!?!?!?
3. In answer to your question: this a matter for Arms and Service Directorates (A&SD), not the AFPRB. Individual A&SD staff their requirements, with justifications, to the JSJET, who then validate and approve (or not) the request. It is slightly more complicated than that, but essentially right.
You state 'GCS Close Support'. Which trade group do you mean:
Gunner AS 90
Commando Trained Gunner
Gunner Light Gun
Para Trained Gunner
or do you mean 'ACS' or are you talking about 'Ground Control Stations' (GCS) which are a Phoenix component. Please clarify, and I (or someone else) will post the info you need.