Could you maybe run a hypervisor with both operating systems? Like one does on a server?

Or will that munch your battery?

Official Android with Google Play and all the things some apps require will almost certainly refuse to run if a hypervisor is detected. Maybe someone could get it to work, but it would be a struggle to stay ahead of whatever new security checks are added to the OS and apps. The point of having one perfectly normal phone would be to not have to worry about any of that.