At the stage where I need to program the ESP8266 and see what it's capable of... time to build a development board.

Started working on one here: https://hackaday.io/project/3352-esp8266-development-pcbs ... As you can see, my current projects are interrelated, working on one, progress all of them...

It's highly likely that the ESP's on-board controller can handle all the sensing and remove the need for the ATMega328...