Don't really give much of a ____ about which of these takes it. I'm just voting for everything that's not Illusion if i'm being honest, since I believe that even something as controversial as No Guard satisfies the concept better than Illusion.
I don't like Moxie and Illusion too much and i think they have too risks or too rewards. No Guard is an explored ability outside of Dynamic Punch, we can do a lot of tricks like someone has already demostrate Grass whistle/Hypnosis or simply a special side abuse of No Guard (who wish a Focus Blast and not a Focus Miss ???)
I'm actually not very up for any of these because they don't put much at risk. Moxie doesn't have risks because it only involves KO-ing and No Guard can be abused. Illusion... I don't get how it's risky, if anything it's pretty beneficial without risk because it can force switches easy.