The proof of concept version uses an Arduino Uno, USB Host Shield (generic) and an ESP8266 (ESP-01S) with a level shifter. The Uno is using a sketch modified from the FTDI example provided by the USB Host Shield 2.0 library. This library supports the MAX3421E USB host controller located on the USB Host Shield. The FTDI example sketch required very few changes to get the UNO and shield to work as a USB host to serial bridge. The USB Host Shield 2.0 library seems to work well and it's still receiving updates.
The ESP8266 is flashed with a Wi-Fi to serial bridge program, of which there are multiple to choose from. I tested the binary releases of ESPTerm and esp-link with no issues. They both offer a browser accessible terminal, and esp-link offers a telnet connection on port 23. I also tested the WiFiTelnetToSerial.ino example included with the ESP8266 Arduino support package. The only required changes to the sketch were setting the Wi-Fi credentials. It worked perfectly as well.
The next step is to replace the breadboard with a prototyping shield stacked on the Uno.