I don’t have a USB AC56, because I just found it too expensive. But form the info on the web it has an internal antenna instead of a second external antenna, but you’ll find several reports here there folks did replace it. So, yes, the electronics is there and the USB AC56 can be modified to a dual external antenna system.
that’s probably a goto thread for the USB AC56: ASUS USB-AC56, wiring, antennas, etc