All the modularity one would ever need is a robust mechanical interface for the back side cover and a ribbon connector standard for internal USB (a convention m

All the modularity one would ever need is a robust mechanical interface for the back side cover and a ribbon connector standard for internal USB (a convention might even be enough, e.g. "microSD with wires"), or at least power. The mechanical challenge of integrating your combined pong controller wheel/tire pressure gauge (or whatever your personal long tail use case might be) into a custom made back cover would be the excuse for existence all those dust-gathering 3D-printers have been waiting for.