After a little further reading of that post I linked, while not clear, it looks like one can possibly load and run separate code on boath ESP8266 and UNO (via SoftSerial)… but you have to keep switching the DIP interface back and forth for programming??
Anyhow… @etabeta If that dual running MCU function does work, then in theory it could be treated as a standalone ESP running Blynk with a softwareSerial link to non-Blynk code on the Arduino… Sorta simular to this - Turning "Old" Arduinos into Perfectly Usable IoT Devices
But not really practical… and despite my attempts to do something similar, it is NOT a process you will get much assistance with from here.