So what my question is.
Can you change so Windows detects your Arduino Leonardo board as another device (like Wi-Fi Adapter USB) ?
I have heard some people doing that and looked into it myself and I can change the PID and VID also the name no problem in the board.txt but that still doesn't change the way Windows sees the device.
The Keyboard and Mouse are "HID" (Human Interface Device) types. You need to create whatever type of interface a USB WiFi Adapter is. I would use Google to look that up. Then I would use Google to see if anyone has done it with an Arduino Leonardo before.
Can a USB WiFi Adapter move the mouse? I don't think so. You can show up as both but if you remove the Mouse device you won't be able to act as a mouse.