You can load the ESP8266 with whatever you want. It's a wifi chip and MCU all in one.
I realize this project has a specific purpose, but I do hope someone makes a version of an ESP8266 board that resembles a .6" dip chip that can be easily breadboarded. A 24 or 28 pin version would probably work.
Break out the ESP8266 fully on one half of the chip and on the other half, include a 3.3v regulator and use level shifters to allow for 5v logic and serial.