I have a variation using both of your theories - feel free to poke holes in it.
I've always thought it was significant that KC ditched the car at Amscot midday on a
Friday. We know she doesn't totally plan things out, so maybe she assumed Amscot would be closed Sat & Sun, hoping it would be stolen. (This would have turned the trial inside out, because if it were dumped, there would likely be fingerprints on it from an unknown party. She could have claimed she picked up Caylee from Zani & someone hijacked the car & took the baby. Remember, no one outside of TL knew the car was at Amscot; he was out of town, so she could have told him she picked Caylee up while he was gone.) Still with me?
Anyhow, she took the guys to the airport early Monday and arrived at Amy's house around 9:45 am to buy gas cans. Maybe as a backup plan to torch it somewhere if the car is still there. However, she goes back, sees the car is missing (already towed at about 10:00) and ASSUMES it was stolen. Probably didn't figure it would be towed so quickly. She sits back & waits for LE to find the stolen car & trace it back. Then she can play her kidnapping story, covering the evidence in the trunk, etc.
However, having the car towed/retrieved by her parents threw a monkeywrench into the whole thing.
It's bothered me that how could KC explain having her car & baby stolen for several days without notifying LE??? But hey, she didn't report Caylee missing for 31 days, so she could've spun a variation of her Zani story. The only difference is that there would have been a dumped car somewhere
with someone else's fingerprints on it. Leading to a reasonable doubt.
I welcome your comments