I was involved in a Cisco networking program for a couple years so I know the general idea (working with those kind of switches and routers is a tad different) of what has to happen here. My concern is what kind of time window do you have? Like, okay, you've got your edited rencrypted .pkx file, there's no way to pause the transfer so ideally you broadcast the edited packet as you activate a wondertrade in game and hope it catches?Ettercap, windivert, winpkfilter.
I feel like I'm missing something very important here.