Is it possible?
Probably, but not owning one I can't swear to it. I'd really appreciate someone trying to rip their firmware and sending me a copy.
Download
PRSCustomizer and send me a copy of your image files to study. Do
NOT attempt to customize your Reader. Choose option #3 and see if you can backup your firmware to send to me. This should be a no-damage-possible thing for you to try.
Thanks!