I think the ESP8266 supports operating in SDIO mode, it's the descendant of a chip used to add wifi to low-end tablets. So it could be used as a literal replace

I think the ESP8266 supports operating in SDIO mode, it's the descendant of a chip used to add wifi to low-end tablets. So it could be used as a literal replacement for an on-board WiFi module, if SDIO pins are available on the Orange Pi board.