Actually I think a better idea could be a common chassis. The common chassis could provide power, (touch)screen, buttons, audio, IMU, NFC, light/distance sensor

Actually I think a better idea could be a common chassis. The common chassis could provide power, (touch)screen, buttons, audio, IMU, NFC, light/distance sensors, barometer, thermometer, cameras and leds; it could connect to the motherboard through pogopins using USB-C standard. This allows video, power and USB hub to expose the rest of the hardware to the mobo. The mobo could have slots in the back similar to librem-5; theses slots would hold sd, wifi and modem cards. I foresee 3 groups for whom this maybe interesting: pine64, purism and fairphone. I really think there is a market for a common platform to make linux phones competitive against alternatives on price too.