Actually, as long as the balas are big, 8 to 10 inches or so, they'll be fine. I've got a small school of them in one of my breeding systems, but all are over 8" long.
Pleco's will sometimes suck the slime coat off a ray.
Tinfoils I've found like to bite ray disks......these were big tinfoils, about 10" or so.
Basically, if the fish can fit in the ray's mouth, it will eat it. Anything big and not too aggressive is usually fine with a ray. The aro should be fine as long as it's big enough (no baby aro's with rays).
I haven't had experience with the other fish you've got listed.
Pat
Amazon Stingrays