>> often trained to administer drugs and other things
Not in the clinics I've seen. Maybe in full hospitals, but in my area the majority of MRIs are at small clinics where the staff are adamant that they cannot handle any drugs beyond contrast agents.
> MRI staff lack the medical expertise to supervise drugged people
They don't, in fact they are often trained to administer drugs and other things (like contrast agents)
> unconscious patients already secured on gurneys
That's a level that might require an anesthesiologist.
Some places offer mirrored glasses at a 45-degree angle, allowing the patient to see outside of the machine. This often reduces anxiety.