This idea is very much a solution in search of a problem, and now there is a problem that is worthy of being solved this way. A robot that is cheap as dirt, but as smart as the average SmartPhone, with all the phones sensors available to detect collisions and tipping (accelerometer) and direction (compass) and position (GPS) and recognize objects and avoid obstacles (camera, possibly with the laser line structured light trick and with cloud services or even vision in the browser via OpenCV.js) all while retaining the WiFi connection to the net for true teleoperation. More about that here:
These are untested and I would very much like your feedback on them. If you see bugs, please let me know. The silence on this project has kept me from devoting any time to it, but please know that if you ask, I will respond and make corrections, etc...
I'd really like to work on a design for a little board to interface between either a shift register or a microcontroller. My idea is that perhaps one board can be made to serve both functions. e.g. You populate part of the board for I2C, and you populate a different part for a shift register.
The other option is to do two separate boards, in which case I would do the I2C to uC version first. It would be something like my RC Servo to uC adapter board: https://hackaday.io/project/181972-rc-servo-adapter but with locations to mount the electronics and 2 light sensors, either directly to the PCB or via wires. (note to self, remember to include strain relief holes. I always forget those).
If a final circuit for a shift register is tested, then I'll try to include a 3rd sensor and use one edge to pinout for a shift register chip.