I very highly doubt that chameleons exist in the wild in their own tree, free from other animals. They must have frogs, lizards (yum!), birds, primates, etc in their space regularly throughout the day. Sure, some become lunch.
I do agree it probably adds a level of stress and irritation, and I wouldn’t consider it with a 24x24 or 3 out of 4 of my chams. The nosy be is in a 45x22?x48 bioactive enclosure with moderately dense foilage im the bottom. He never goes to the bottom or hunts the giant canyon isopods which are close to the same size of the mantellas.
I think once the plants are grown in, I’ll be able to introduce them without issue. I think the panther may be more annoyed with me than the frogs... which is a good point. We stress the animals, too!