Could you please tell me who is the Wi-Fi module / Chip vendor? Also, what is the interface for the Wi-Fi module (SDIO/USB/PCIe?)
If you don't need the Wifi module, its 7-pin header can easily be used as a fourth USB port-- just skip pin 1 (closest to the rear of the board), and starting with pin 2 the signals are the same order as for USB port 3 on the 4-pin JST header: +5V, DN, DP, GND. See page 10 of the schematic, lower-left corner. The only caveat is that the +5V power connection on this header, unlike the other USB ports doesn't seem to be protected by a fuse, so adding an in-line one somewhere between the header and your USB socket would be a good idea.