one of ideas to try is using esp8266 SDK AT firmware with Uno WiFi. the <lib/SC16IS750.h> contains a Stream implementation for communicating with the esp in a way as SoftwareSerial is used with esp modules.
and there would by the possibility to switch to what I call 'straight serial'. the communication with the esp would start over SC16IS750 and the sketch could set with AT command the esp pin 4 to LOW to switch to straight serial.