"Obviously, those medically diagnosed with a mental illness."
What is obvious? Google the DSM-IV, the book of psychiatric diagnoses. I think you will be shocked by the hundreds of diagnoses you will find, the majority of them having nothing to do with hallucinations, delusions, or psychosis in general. How about learning disabilities for one? Hmm?
"I would hope that that person if a gun owner will consider legally turning over their guns to their siblings/family members considering the mental impairement that person faces."
That they face? No sir, I will not accept that proposal. It could be many years before the person loses their ability to functional normally. They might forget some things, but still drive safely, work and even continue to run a business.
"Temperment, mood, personality are other things altogether."
You really need to look at the DSM-IV. Those three things you listed are NOT other things altogether as you put it. They comprise a large number of psychicatric diagnoses - see the chapters on mood disorders, personality disorders, etc. And you want to ban firearm ownership because of all of them?
If there are restrictions they need to be imposed because of behavior, not a one-line code and diagnosis in a medical report.
John