Re: What would be a safe media for...
Soda Blasting. Google it. You might be able to find someone in your area to do it reasonably. It's gonna be easiest on the aluminum and not produce the damaging grit that sand/bead blasting would.
I think that soda blasting takes specialized equipment so if this is a DIY project then JB's idea would be the best for you.
Also, you do not need to blast off every square inch of old paint. Just do the parts that want to come off easily or shows any corrosion underneat. Wash any bare aluminum in commercial prep or vinegar, zinc chromate the bare spots, overprime with a good poly catalytic primer then go for your top coat.
