I've been working on this for a few days and it's now at a stage I feel at least comfortable presenting in its sandbox format for critiquing, cries of "OMFG, another [random SCP number]" and other comments.
Could use better containment protocols- once the face changes, why not set off a few flashbangs in the chamber? If you can't find someone staggering around dazed and half-blind in the first minute, an automated mechanism will jam an metal spike into the dummy's ear and wiggle it.
Because if a visiting member of O5 happens to bump his knee in the toilet and isn't found in time, I'm quite certain the guy pushing the button to have spike inserted in the dummy's ear will have to answer some pretty serious questions. That's the point of the dummy. It doesn't discriminate.
Also, the flashbangs wouldn't do anything unless they also caused burns.
And edit the nth: I clarified it needs to be a physical injury.
However, after getting the people in chat to look it over I've changed my mind. See, if the object's stored in a Storage facility near other SCPs, the danger I describe above is very real. If it's stored on the compound, far away from areas where personnel and other SCPs are, there's no such problem.
The flashbangs still wouldn't do anything, but doing something to the dummy that would only incapacitate the subject imprinted on is still a good idea. Shooting it in the leg for example.
The long and short of it, you're right.