The question that comes to mind instantly is why? Do you just not like either plant? There is likely no better ready available plant for a chameleon that WILL eat foliage than the hibiscus. Pothos would be a close second. Umbrella being my third. I would caution against the ficus with know plant eaters. They produce a defensive secretion when broken that is mildly toxic and can cause skin and eye irritation.
If you are very ambitious set up an aero-hydroponic system in the cage and grow romaine, kale, and collard greens.
Sure as heck someone will come on with a 30 year old veiled that eats nothing but ficus, so before you say well so and so said ficus is safe please go read the poison plant databases.