Firstly how severe should a taken out result be for example is Darth Vader's fate (permanent life support machine) an appropriate take out result for a PC.
I'd see this as an "Extreme Consequence" -- something that alters the High Concept of the character!
Yeah, Anakin was "Taken Out" in suffering this consequence.
And yes, this IMHO *
IS* something that -- with general group buy-in -- can be applied to PC's.
The question really needs to be addressed up-front, alongside several other issues. DFRPG is one of the games where "everyone on the same page" is rather important!
- What level of intra-party conflict is allowed? Are PC's who are liable to kill (or meaningfully undermine) one another OK "within the group"?
- How much of what kinds of violence are allowed? Might there be a serial-murderer as a villain? Serial child-murderer? Serial rapist? Etc... Quite a few people will say "NO" to some of this (I probably would, myself).
- Can "worse violence" than happens in-play happen via brief no-details GM-narration, establishing the villainy of the villain without getting too graphic/squicksome?
- When a PC gets "Taken Out," what sorts of results *might* that mean? Permanent death? Permanent maiming/scarring? Life-long life-support? If it happens at a REALLY climactic story-arc culmination, is self-sacrificing success ("win" the issue, but die) OK?