You are better off posting this on the military forum unless you already have?
If you are serving in the RE why don't you get information on the AAC from within the Army? If you did you would know that you do not 'transfer' to the AAC - you submit an application for pilot training. Then if you are accepted, pass the course and serve in an AAC unit you may get the opportunity to transfer.
You'll still be a soldier first and a pilot second in the Army so don't expect any great improvement in your living conditions etc. You will still get stuffed around and shake your head at gross incompetence. Pay will be better because of flying pay, rank and pay band and you may be treated with a little more respect.
If you enjoy military life and want to fly without having to get a commission then NCO pilot in the AAC is the way to go. I loved it.