It's difficult to "opt out" of GS pay scales, and even then if you do you then have to follow different recruiting patterns and are subject to fairly strict guidelines. They do have special scales for special positions, but from what I understand that takes awhile to establish and still has strict guidelines. (http://apps.opm.gov/SpecialRates/2014/index.aspx)
Federal recruiting can be quite a minefield, which is a significant problem in fast-moving professions. According to this article the NSA don't opt out of the GS scale, but that's not to say they don't offer temporary positions with slightly different criteria: http://work.chron.com/nsa-pay-scale-16399.html
I'm unsure if it's different on the military side but typically that pay / Basic allowance for housing / etc is also clearly defined in advance.
Federal recruiting can be quite a minefield, which is a significant problem in fast-moving professions. According to this article the NSA don't opt out of the GS scale, but that's not to say they don't offer temporary positions with slightly different criteria: http://work.chron.com/nsa-pay-scale-16399.html
I'm unsure if it's different on the military side but typically that pay / Basic allowance for housing / etc is also clearly defined in advance.