Yes, though I would advise that you are fairly experience with keeping discus. Also only go with healthy adult or sub adult discus. You would be limited to either a black or silver aro, jardini would likely not work. Can't coment on lei's or afro's and asians are illegal.
As long as the discus can't fit in the aro's mouth, it should be fine. Of course aros are large carnivorous fish that produce a lot of waste, and discus are extremely sensitive to said waste, so that could be a practical concern.
Keep the Aro very well fed and lots of space for the fish along with a great system to take care of the waste and weekly water change ( depending on system )