The new Tractorman scenario actually makes a lot of sense to me, since it possesses a clear motive (retaliation against the park by a disgruntled employee after being sacked) and a clear opportunity (by a very knowledgeable perpetrator with specific information about the park). How can one best retaliate against a vacation park, well just induce a terrible event like this and bookings will drop to zero. Al it needs is: observe the families from the car park near the Ocean club entrance, enter through the open patio door, suggest the kidnap by opening the window, snatch the child, leave through the front door, go round the block (per sniffer dogs), check whether coast is clear on the uphill road, cross the street when the coast is clear and walk to your car in the car park (where the sniffer dogs lost the traces). After that anything could have happened of this in principle innocent 'kidnap', but the bizar media frenzy in the following days might have scared the kidnapper so much, that he decided to kill Maddie and hide her body forever.
How much simpler can we get?
Before you say that disgruntled staff doesn't do this, note that disgruntled employees can do very bad things to the company they work for (famous case in the Netherlands where Ferdi E. kidnapped and killed one of the Albert Heyn CEOs. Motive, revenge to his former colleagues and no relation to Albert Heyn)).
And hey, he might not have had murder intentions at the start and only wanted to suggest a real kidnap to damage the park's reputation, but actually the McCanns calling Sky and inducing the Frenzy could have forced him to it in the end.
Why are there no traces of this man in the apartment, simple, he wore gloves. And secondly, because so many people (20+) were running in and out the apartment before forensic managed to seal it off, that so many traces were disturbed and lost anyway.
Also, the car park from where a man has been seen observing the apartment earlier in the week, is an ideal to spot to park your car. You can easily observe the movements from all the parents and wait for the right window of opportunity. Also nobody will see and connect your car directly to 5A (contrary to when you park it in front of 5A). Then the front door exit is much safer as an escape, since if you would encounter one of the parents coming up, the patio door exit is risky since you'll meet them head on. Also turning left, rather than right (shorter route) and then going around the block is much safer since you minimize the distance (and the risk of an encounter) between the car park and your location at the end of the foot path in front of 5A.
And maybe the suspicious Tractor accident was suicide induced by not being able to cope with the tragedy anymore...
It all fits and could be the real deal.