Unfortunately, the site you're ultimately referring to (not HTC Geeks) 'charges' too much for me, being a hardware person. Too bad - lots of good info.
However, with that said, why don't you have a go at this. Essentially, what we're looking for is the USBOTG driver that we can port to the X51 series under WM5 or WM6.
The Client USB interface uses the USBOTG hardware interface already. The new driver would need to disable the client interface and take over that particular port. It should be doable.