Okay, this is a theory that my DH I have been throwing around. Do you think KC could have disemembered little Caylee? Or attempted to? The reason I initially thought of this was the fact the skull "rolled out of the bag" and the news reports were at first saying "only a skull" was found then LE said they found "full skeletal" remains.
I know it's horrific but maybe she attempted to do this and used some tools in the house. LE would have been able to see cut marks on the bones when finding the body if this is the case.
I don't believe for a second KC cared one bit about this baby. I don't think she put any crosses or any items that showed she was "motherly" or that she cared. I don't think she put a paper or note in to frame the nanny. Remember folks, the nanny story didn't come out until LA & CA were questioning her about where Caylee was the day of the first 911 call. If you read through the docs that were released, especially LA's interview (#3 I believe) it talks about this.
She just makes things up to suit her situation at the moment. The nanny stuff really grew that day. And if IIRC the boyfriend and others hadn't ever heard of the nanny's name, just "nanny" not "Zanny".