As far as mental disabilities go, I don’t think it would be a very great idea, especially if it’s for no other reason than to be relatable. Basically what Doot said:
However, that being said, I would very much like to see physical disabilities in Matoran, and seeing how they can overcome them with the resources that exist within the BIONICLE universe.
Imagine a Toa whose legs were paralyzed, so they use a Miru to levitate as a means of getting around, or a blind Toa with the Arthron a la Daredevil.
Implementing physical disabilities could open up possibility for some creative ideas and unique character traits. And overall, giving a character a physical disability and a clever way to overcome it has much less potential for controversy; Not to mention the risk of misrepresenting a mental disability and offending those who actually have it.