Shared 5v power for Due dedicated application I would appreciate input on this situation:

I plan to power a fairly high current, 5 volt supply, 3.3v signal, device from a suitable wall wart. I would like to power the due that controls it through the due's usb port by tapping the 5v from the wall wart into a suitably modified USB cable (leaving the signal pins unused). No significant external power demands would be made on the due's 3.3v or 5v headers.

So there are two devices sharing the wall wart: one device that uses high current, and the other device is the due.
Yes it is possible. You just need to connect both Grounds