You would need to write drivers to make the USB-Port with the rest of the Hardware. There literally hundreds of different WiFi-Sticks.
I'm aware that USB doesn't supply enough power (but I'm spoiled with USB-C nowadays of course). And as I mentioned, I'm happy with the solution I built myself. I don't care if there is one more power cable in the back and i don't need the remote. I just wanted to give feedback, that this router does its job.
Thanks for the feedback on the router! I'm looking at the slightly older 702 version as it's half the price, and as it has access point mode, it looks like it should do what I need.