This goes back to my own rule of thumb on maneuvers. Without a LOT of good reasons, I do not allow aspects from maneuvers that can not, in turn, be countered/removed by another maneuver of some form. "Beheaded" or "Disintegrated" certainly fall into that area. I leave those sort of permanent, life altering aspects to come from consequences.
Which, if you are a good swordsman capable of decapitating a person with a single swing of your blade in combat (which is HARD folks regardless of what the immortal members of the Clan Macleod has taught us) you can do that as an attack. Mook flubs a defense roll, netting you a +4 on your attack roll with a Weapons skill of 4. Added to a weapon rating of 2, that is 10 stresses to a mook that has, at most, 3 physical stresses? He's going to concede most of the time and go right to Taken Out unless your GM is being nasty with you.
I would discourage the use of Maneuvers that give life altering aspects. After all, maneuver aspects are usually fragile. How does one come back from "Beheaded" after the aspect fades away?
- "Turned you into a newt?"
- "Umm... I got better!"