Seems like a simple solution would be to carry two phones. If you are stopped hand over the clean one keep the real one out of sight.
Simpler would be a 2nd way to unlock the phone into a fake user account...
The main thing is it is nice to get away from the main phone on a trip and enjoy the trip. Losing it would not be the end of the world.
All these other aspects you get for free.
Are you just living in the "second OS"? Meaning you don't actually use your phone while you are outside? Or are you going to just casually reboot your phone and boot into the "second OS" while the officer is standing there demanding your phone?