Most likely? No NPC will have either this Charm or the ability to produce sorcerous body doubles. This Charm is there to represent a gimmick of the greatest artificer in the setting, in case you would like to, say, play that character. It's there as a canonical example of the kind of unique greatness your character can achieve. There are others. It's entirely possible no one has done it before, and no one will ever do it again. (though they may well achieve their own unique peaks of greatness!)
I know, this is offending to the sensibilities of some. Shikata ga nai. Different people have different tastes.
Sore ga tasuketa koto ga dekimasu. (Arigatōgozaimasu gūguru transratru!)
When I GM games, I like to have the book assist me in doing so. For example, when I want to use a Solar as an antagonist, it's nice to have a list of a bunch of stuff a Solar can do to draw from. Maybe, strictly speaking, no such thing as a 'Charm' exists, and the stuff called a Charm is just an abstraction of the kind of thing a Solar can generally do - whatever, I just need to know what kind of stuff Evil Solar Dude can do. I could just make shit up, I guess, but I could also make the entire
Exalted setting up too; the books are there because I'd like someone with the skill and time on their hands to save me the effort of making up the
Exalted system and world.
But when you then tell me that "no, these Fancy Magical Powers are only for PCs, NPCs can't use them", that means that there's less Fancy Magical Powers in the book for me to give both Evil Solar Dude and Helpful Solar Ally. By the rationale you've presented, even, if there are
two characters who want to play the Greatest Artificer in the setting (let's call them Urza and Mishra, and say that their rivalry is legendary), only one of them should pick the Doombot Charm, because it's a unique power.
This means that the overall
utility of those Charms is reduced, because the part of the page one of these Charms occupies becomes effectively blank the moment someone picks it. It's a piece of the book that, for the rest of the game, I can't use to make more Evil Solar Dudes or Helpful Solar Allies. The moment Urza picks the Fancy Magical Power of making Doombots, Mishra has less options left to pick from. And while, to some degree, different people have different preferences for how games should be run, the kind of people who
do enjoy narrative mechanics are generally not kicked in the stomach by mechanics that don't emulate narrative conventions (like, say, having the Doombot be something you have to prepare in advance), but to the kind of people who
don't enjoy narrative mechanics will find their enjoyment diminished by their inclusion,
if only because it means they get a dozen Charms less than everyone else to play with.
So it can be helped. It can be helped by making a game that, simply put, has a wider appeal. And this isn't some grand-scale "dumb it down"-thing, since we're talking about the third edition of a game here, and the previous editions didn't have retroactive narrative Doombots in them.
(Also, lawls, they're a year behind schedule, and writing unique niche one-use-only Essence 5 Charms is something they're actually doing.)
However, it is extras that cannot stunt, not NPCs, though an NPC stunting starts to get into iffy territory since the ST is the adjudicator of how much a stunt is worth.
A GM is also the adjudicator of everything that says "unless this would be blatantly impossible" and what the exact definition of "a creature with four legs" is. Stunts are covered by the rules; using Exalted 1E as an example, a 1-die stunt describes an action with sensory language ("I hit my opponent with my mace and it makes a loud clang.") without repeating a previous stunt, and a 2-dice stunt also involves the immediate surroundings ("I blackflip off a nearby wall with a 'thump' and hit him with my mace."). Unless the ST starts blatantly cheating or is always awarding his NPCs 3-die stunts, it's hardly iffy.
