CPS, I understand that you like that the rules support the ability to play unsanctioned psykers. The system gives you the freedom to play one with any character combination that doesn't include AAT. The problem myself and other people have is that the current rules take away the freedom to play a sanctioned psyker from non-AAT backgrounds, something which is also more common in the fluff working for the inquisition than unsanctioned psykers are.
I'm perfectly fine having the freedom to play an unsanctioned psyker. I just want more freedom for playing a sanctioned one. In this case I think you would maximize choices by making psyker ONLY be an elite advance, same as untouchables. Make it cost 200 or 300 xp and be sanctioned by default. For 100xp less, the psyker doesn't start off sanctioned. Rework the mystic role around a bit to make it a viable choice for anyone. Now you suddenly have opened up a lot more options for players wanting to play psyker characters during character creation.
Doesn't this proposal just complicate a system that is being handled elegantly?