I already have the games I wish to use. I have looked at the source code for wupinstaller-y1.3
main.c
Line 48:
"dirPtr = opendir ("sd:/install/");"
So i could potentially recompile with a defined USB device and install from an external from there.
It would be better to get the source code for WUP Installer GX2 however and I could modify it to read install folder from multiple locations.