So essentially the argument here is whether : FAQ > BRB FAQ> Codex > BRB OR FAQ > Codex > BRB FAQ > BRB?

I always considered the reason they put the ruling in the BRB FAQ was to cover all instances of +1 or whatever to Reserves, since the Astropath is NOT the only thing that can do this. I've always been a fan of Codex > BRB.... But I have always considered the BRB FAQ to have a more definitive ruling than the Codex, since the FAQ is more recent. The IG codex was written when taking them as Allies or taking Allies with them didn't exist or was limited to archaic codices such as Daemonhunters and Witchhunters. I guess either GW will have to FAQ this ruling or state definitively the priority order that the FAQ's and Rulebooks go into. Otherwise I see this thread going around in circles :P