I'd be okay with mental health data being used in NICS on a must-report pass/fail system. The psychiatrist is obligated by law to report mental disorders known to be at risk for violent behavior even without an immediate risk to the patient or others. The gun shop owner knows he can't sell, but not the specific details of the customer's mental issues.
I personally have no objections to the AR-15. Its a mean looking gun comparable in power to many, many other less mean looking guns.
With your listed caveats, I'm fine with whatever guns you want that are currently legal. Registration being key, which will never pass.