Look in to Android Developer Debug Bridge, atleast in theory connecting the phone to a computer via that method should enable sideloading apps regardless of what obstacles Google might try to create. In the long run though, the solution has to be proper x86 laptops which can run a totally normal Linux distro, but so small they can fit in your pocket as a phone does, with inbuilt radio modules to connect to phone networks and WiFi for data, and a high efficiency hold-everything-in-RAM-but-do-nothing sleep mode to get around the inefficiency of x86 chips for low power usage.