Below is purely based on past discussions/ideas, hopefully someone else on here is close to the program and can confirm/deny and/or add info...
A major intent is to maintain the CAS/Sandy culture in the AF; we do not want said culture and the dedication to said missions to die when the Hawg goes away (whenever that is). Think of it as the AF's idea of maintaining a "CAS/Sandy heart beat" and not letting it shrivel to "just another mission set" the Viper, Strike or Fat Amy does. Additional plans are to move the Viper FAC(A) school house there from Luke, as well as start up a Sandy school house (whenever the mission officially transfers from A-10 to F-X). Always a potential for A-29 type aircraft to someday be added to the inventory, and this group would be an ideal location. Perhaps in the sunset of the Hawg, we'll see only 1-2 squadrons remaining and they'll be moved to Nellis to be a part of this group until the end...maybe. In addition to the air side, this will be a central place for the JTAC community to maintain/develop their side of the mission in an environment that is focused all on that, and not like it is currently where a lot of JTACs are holding signs on the side of the road saying, "will go TDY to random ranges for controls." That's the very general idea of it - hopefully someone else has more current, in depth knowledge to pass on.