Botia striata may work. I haven't tried the combo yet but may in future. There may be risk, loaches may carry nematodes. I treat all mine in QT just in case. Clowns like the discus temp but are nocturnal, spooked my angels, so I won't try that again with discus. Pinkertd had y.sidthimunki with her discus but took them out, I think because the big discus made the sids hide, not sure...Debbi? Yoyos & histrionica maybe be too rowdy...
Have you tried other methods of snail control? Loaches need a social group, most like stronger current than discus. You can squish snails against the glass, bait & remove...a few are no big deal.