I'm going to try that. However, does the person in question need to be alive when the PC walks in and then dies? Basically, what I have going on is there is a room in my mod where a "doctor" was killing ghouls to make certain items. So, the ghoul on the table would already be dead prior to the pc walking in.
It depends of what you want exactly. You could create your creature already dead (just give it 0 health), place it as you wish on the operating table in the GECK with F4 CTRL-Alt and add a script to dismember it on load. Tweak the one already in the GECK to make yours just to remove the head
I never tried with creatures, but with characters it works.