I am no longer in the Aviation field, but up until about a year ago I was a 15R for the previous 10 years. I decided at year 10 it was time for a career change, so I reclassed to Intel. Usually I would say that having your A&P wouldn't help you, however there is the program in the Army called ACASP. I'm not sure of the specifics for it so my recommendation to you is to google it. I think Aviation was/is a awesome field to get into with the Army. God knows people there seem to be much more normal than the people I surround myself with every day now. If your looking for real crew cheif/flight time then I would suggest either 15T or 15U. 15T's have a few more duty locations open to them, but in my personal opinion any of the jobs you listed are limited in duty locations. For my first 6 years in the Army I was stuck in the Savannah, Ga, Korea, Iraq rotation. Now I have quite a few duty locations open to me in my new MOS. If you sign for the job you are locked in for that job. If for some reason you got to AIT and failed out then it is possible you could be reclassed to needs of the Army. Sorry I don't have more indepth info for you, but typing on this little keyboard is getting old.