I guess the main difference between a FA becoming a CSM and say a FO becoming a captain, at the moment anyway, is that the FA must apply and be selected for the position, whilst the FO automatically gets a shot at command on seniority provided he/she has jumped all the proficiency hoops.
Technically the FA is applying for a new job and must be selected from the pack. The FO is upgrading the job he already has. So I can't see AWA's for command just yet. It would be a very provocative move by the company.