As to auto-docs doing cosmetic surgery...
If you've read Colin's 2300 AD materials, he talks about auto-fabrication machines -- highly advanced 3D 'printers' that can make almost anything, up to and including most starship parts, if you've got enough raw materials and the licenses to do so. These licenses are what keeps the unwashed masses from 'makering' their own starship one part at a time or ginning up their own FAM-90 Gauss rifles.
I submit that it's not all that much of a stretch to see some sort of system like this in the Imperium. Marc Miller mentions 'maker' units aboard Imperial Navy vessels in Agent of the Imperium.
Taking that logic a step further, I suspect you'd have to dig pretty deep into the firmware and software of the standard megacorp autodoc unit sold to ship crews to get the machine to do full facial reconstruction. And even then you DNA won't change and neither will your retinal scans. You can hide your retinal scans, of course, but your DNA will be much tougher thing to hide.