Is it possible to only have the passenger side view mirror tilt down and have the driver side stay put??

 

No, unless you want to rewire the whole thing and add some of your own control switches, which would be a lot of trouble for not much return. As delivered from the factory, however, that cannot be done, and yet somehow millions of RX drivers are getting by.
Actually, there might be times when that might be helpful, but adding too many variables to the gadgets adds complexity to the controls of all the various devices, and that often frustrates drivers more than not having a feature available. I have a lot of friends whose cars actually have mirrors that do not tilt down when the car is put in reverse, and they would love to have that feature. There is already a fair amount of confusion about the switch that prevents the tilt down feature from activating - adding other controls to actuate only one or the other would give the driver four mirror tilt down configurations, which would be too much.
However, perhaps the car could sense with and IR or radar signal which side of the car had a curb next to it, and then just tilt down only that side??? Then we'd only need an override to tilt it down when we wanted a look at the ground when there was no curb there.
I gotta go.