If the AAC are to be believed only handsome, debonair types are accepted.
It's changed to Aircrewman in the last few months, a review of ACM duties and responsibilities has sparked quite a lot of work in HQAAC.
There will be a joint course held at DHFS and an aspiration of tiered flying pay (I'm not holding my breath)
For selection as an ACM, you have to be a Class 1 AAC Ground Crewman, successfully completed PNCO and DIT course, have Level 2 English and Maths and recommended LCpl and pass Aircrew Medical and OASC at RAF Cranwell.
In answer to the original question, there aren't many AAC Class 1's not in the AAC.