The idea sounds brilliant, but like CraigEllsworth said be careful with you portrayal these mental illnesses. For one thing autism/aspergers are on the same spectrum, but you will find that people with aspergers are highly functioning in comparison to someone with autism. There is actually a movement to separate the two in the DSM:V. Another thing is autism isn't considered a mental illness, but rather an intellectual disability. I'm not sure how important that distinction is, but I think it is important to point out that distinction. A game like this could really give people a window into just an ounce of what people with these problems endure, and I think that is constructive. The only real advice I have is accuracy is key in building the worlds you want to build. You are going to be working with a subject that is really touchy (touchy in different ways person to person) for a whole lot of people.