Just to be clear about this:
I Have a wyse 3020 ThinOs Lite, and I can make it boot DELLWYSE USB created with USB FIrmware updater V2, and it brings a screen to either copy firmware from device to USB or from USB to Device.
So far, I could do Device-USB and then USB-device with the same firmware. I am trying to find some Linux (found the T50 here in this webpage but fails due to mbr.img; it tries to copy it to the device and fails with an error about it being too big (512).