This is what I am betting on. The state cannot force KC to take the stand. But certain defense tactics would force her to do so. It is doubtful if any defense involving ZG or "the nanny did it", would be allowed to be presented unless KC takes the stand. There is no eveidence of the existance of ZG other then testimony from KC. She is the root source of anything on the subject. So all the defense would have to work with is KC's direct testimony, and heresay evidence of others who heard KC tell them about ZG. While the burden of proof resides with the state, the defense is not allowed to present pure fabrication to the jury. There must be some chain of evidence or direct testimony. You cannot simply try and defend a murderer by claiming alien abduction or an act of bigfoot. You need at least one person to swear under oath that they actually saw Bigfoot.
The sad thing is, although I completely agree with you, I think Baez might actually simply try. None of the wiser legal minds on his team seem to be helping him draft coherent motions, so I still get the idea that he's intent on running the show and will eventually run it into the ground.