TL;DR: Just as a proof of commitment, I could send you the schematics and a binary with an initial prototype of the program so you can test. I could do that in a day, for free. Read further, if interested.
Good day. I have plenty of experience designing MCU-based embedded systems. I've worked at Freescale Semiconductors for half a decade as an engineer. I've worked with several arm-based microcontrollers (NXP, Atmel (now Microchip) and STs families) and, lately, with the esp8266 and esp32 family of microcontrollers, either with or without an RTOS.
I'd need more information regarding the exact specifications of the project, as well as your expected timetable. However, I have designed similar projects before and in less than a couple days we could have a final prototype, taking into account any last minute changes.
Regarding payment,of course, none is required before a proof of work (schematics ,sourcecode and other related documentation).
Regarding the implementation, If you need low pinout and medium speed, I'd go with i2c or even better one-wire. I can send you the binaries, the schematics and setup instructions so that you can test it TOMORROW.
I think it'd useful for the both of us, if we could talk a bit further regarding your project's requirements. Once we do that, I can send you an initial solution, free of charge, so you can be sure it works and you could then give any feedback for further improvement.