Theory: in any attempt at making some sort of paper and pencil/numeric KMV system, there would have to be a stat judging how much of a fourth wall a character would have. Mostly, this comes into play in terms of genre-savviness and narrative manipulation as you’d expect, lower being better for that specific purpose and higher probably being better for dealing with NPCs. Well, as you’d expect if you were me.
It probably has some sort of effect on general personality/sanity, too; actually I suspect most of the KMV numeric stats would be used to determine personality, and any combat statistics would be a seperate section entirely. Most notably, in my mind the difference between Helena and her successor is mostly that her fourth wall score is much lower than his; she caught on to the grand truth of KMV strategy* considerably earlier than he did, at the obvious cost in… visible sanity.
As evidence for more stats being needed to determine sanity, a (very small number of) examples for different levels of this scale (a version going from 1 to 10, which might not be the actual numbers, but):
0 – presumably people on this particular earth-prime, capable of switching from timeframe to timeframe/viewpoint to viewpoint infinitely many times
1 – Lancer, James, Nightmare (if alive), et al.: at least Lancer and Nightmare (thus James/Tian) basically got Physical God levels of power by surviving the end of the old-KMV and the beginning of the new-KMV. You can’t get lower than that in character.
2 – Helena (by extension Xanatov), Ignatius, Dale, Elsinore, Elias and Cara: I’d say this is the example for the existence of other personality measurement mechanisms, because honestly. Even using the version of Helena from Sigurd-future and versions of Elias and Cara from some bizarre mirror universe, very few of them have anything in common about personality apart from this.
3 – Julien, Lowen, Tobias, Lunedi, Alexander (actually): Of these, Lowen probably falls closest to rounding up to 2. This seems to be the tier where the sarcastic characters who live because of their use of Mythology Gags and Shout Outs hang out in general.
4 – Mona, Mikkau, Kyle, Laura, Darian, any version of Markellos, Moran: Okay, never mind, this beats out 3 for sarcasm by a long shot. This is also clearly the tier where everyone whose name begins with M is.
5 – Chromus, Miles, Molotov, Sterling and possibly Serena: Mostly the somewhat apathetic characters, for whatever reason. (And Sterling.) Then again it is in the middle of the scale.
6 – Alexander (feigned), Sulla (Wizard-02, Helena’s mentioned replacement), more or less any sort of cosmic horror including IRIS: The characters who, while generally aware of their fictional nature to the point of more specific Medium Awareness, really don’t realize how to manipulate it and its principles to their own ends. It says something about the KMV that these three are the only examples I could think of, despite some effort.
7 and below are almost entirely NPCs; I can’t think of any main or secondary characters who fit, although 7 probably includes your average universal Library Guy. 10 is pretty much complete obliviousness as to being fictional; not even most random townspeople fall into that category, though, due to historical Events.
I assume most PC-class characters would fall between 3 and 6 on that approximate scale.
* Distilled into one aphorism: Good real-world tactics, while they may help in certain ways, really don’t help you as much as strategies weighted towards generating drama can. The KMV is permanently stuck in a deep pit of cinematic rules and nothing will probably change that, ever. Helena’s killsat is probably the prime example of her taking this to heart…