Alright, for now I have given up on getting MKWii Wiimmfi to work on a WiiVC inject. Since it worked for PP7, I'm leaving that as is. For MKWii, I'd still like a one-click option from the Wii U menu, so here's what I've come up with...
Run MKWii from USB Loader GX, via a WiiGSC Channel, via a...