If the scenario I postulated happened, it might explain other things as well. I originally came to this idea because I was disturbed by his original interviews with LE and FBI. Particularly the part where he vomited. It made me think he was having a flashback of something he had not only smelled, but something he had seen as well. So I went back and watched the FBI tapes. I've had to do my share of interviewing, and have been coached by some really good investigators and polygraphers on red flags to look for. One thing I noticed was that GA was being a little too free with some information as if to distract LE. And that he gave far too much detail in 4 different areas (extra and unnecessary detail also often being an indicator of deception). These four areas were: the 16th when KC and Caylee left, the "pool" incident, the gas can incident and picking up the car at Johnson's. Working backwards from there and assuming he might be lying, I tried to figure out why that would be so.
The 16th was easy - it was necessary to possibly corroborate KC's story that she left the house with an alive Caylee that she may have handed over to another person. It would eliminate the house being the last place she was seen alive (or a crime scene) and would introduce doubt that KC might be the last person to have seen her alive as she was ostensibly on her way to a nanny that would have Caylee overnight at least. The detail he uses for her outfit matches the description KC gave on her police report when she says that is what Caylee was wearing on June 9th. Other posters have already found cracks in the theory that he actually witnessed her leaving.
The "pool" incident seemed to me to be a set-up for LE so that, if necessary, an accidental death scenario would seem likely or possible. GA is not specific in his recollection but indicates it was sometime that week. (If it did indeed happen, it might have happened on the 18th, if KC came back and originally thought to bury Caylee in the yard, then gave up and rinsed off in the pool before returning the shovel next door and forgot to either lock the gate or put up the ladder).
The gas can incident seemed to me designed to do two things - indicate that there was nothing GA saw in the trunk and, more importantly, that there was no smell (which would put the body being in it at a later date, possibly after it was towed). I'm quite sure he smelled it and knew what was up. If he chased KC though, I always thought he would have caught up with her quickly, not enough time for her to drive fifteen houses down, park the car, open the trunk and dispose of the body without him seeing her. I don't think she would have risked that kind of time line either. He certainly knew something was up by that point though.
His description of picking up the car was the most damaging, imo. He explains to the FBI he thought it could be KC or Caylee (he knew immediately it was not KC because the car had been at the towyard too long and she had been heard from since then). He describes getting in the car, putting the key in the ignition and saying "I'm doing this wrong", whereby he gets out and uses the guy at Johnson's to be a witness to the trunk. I have a feeling he knew that it would be empty - had figured out maybe from the gas can incident that if KC was hiding something it would be in the wheel well, as she had had flat tires several weeks earlier (she gleefully mentions this in her visit with GA and CA as well, as if she has caught on that somebody knows about flat tires). He is relieved that the guy at Johnson's smells the car but sees a bag of garbage and throws it over the fence. GA has a witness to an empty trunk and he can drive it home and work on it from there. If a body had been in the trunk, he could have called LE right there (instead of paying hundreds of dollars to retrieve it) and claimed it had been stolen and used in a crime. I'll bet he was glad he didn't have to.
I think he sent CA to work right away because he did not trust her ability to keep her mouth shut (she still told everyone at the office and later told the 911 operator about the smell). He had plenty of time to report to his office at work (using the EZ pass route he mentioned in his interview would check out the car chase) and coming back home a back way - spending an hour or so cleaning the car - returning to the security office and from there taking an EZ pass route to the mall to clock in by 5:30. However, it's odd he only worked half a shift, returning home about four hours later right when it was all hitting the fan.
In the jail visit, CA looks at KC as if she is a hawk looking at a rabbit, and grills trying to see if there is any way that KC might have simply given Caylee to someone else - eliminating that as a possibility before she allows herself to think of Caylee being dead. GA sits and fidgets and looks almost bored in those interviews. His "hi gorgeous" may have been his way of trying to let KC know he was on her side and was willing to help her get out of there on a lesser charge if she cooperated. KC finally figures it out in the last visit and requests to see her dad.
If LE figured out that GA might know something - or could get KC to talk - they might have been watching and sympathetic. They certainly had to think his interviews sounded conflicted and odd.
I think that when CA found out about all this was in November. At the end of the week of November 7, Tim Miller had called off his search rather quickly and LP put into effect his JBP stunt. It was obvious that LP would keep searching. That next weekend, DC suddenly got specific information about where Caylee's body was and it coincided with the orchestrated diversion of the "Caylee sighting" at the mall and the subsequent presser (in which CA looks positively drugged and is listlessly crying and clings to a GA that looks confident and in charge).
Well, I've got more but I've rambled on enough. I'm still very open to alternate scenarios but this one has tied up many loose ends for me so far. I think GA's instincts may have been good, or at least something he felt he could live with - to protect his daughter from murder one, but to have her finally pay by pleading to a lesser charge.