I am not sure how that would shoot the theory down, it definitely doesn't in my opinion.
Prayers for HaLeigh
That someone would stage the MH to look like an abduction, take Haleigh, leave Jr and have people discuss that this was because of a future custody battle? ok.
Or the one about staging the MH to look like an abduction in order to rescue one child from harm and leave the other in harm's way? ok.
Theorizing that someone in Crystal's family could have taken Haleigh for either of these purposes means that this person had to have been made aware of the layout of the MH, the sleeping arrangements, Misty's habits for sleeping, the best way to get into and out of the MH without being detected by neighbors who may be looking, putting themselves at risk of discovery in both the entrance into the MH as well as the exit out of it, not to mention having to deal with Misty should she still be awake. Risking that Misty would have awakened at all seems a risk that only a fool would think of taking....not necessarily improbable, of course.
There is only one way to that trailer from Buffalo Bluffs road. Only one way to get away from it. There are two doors into the trailer. Both doors are visible to neighbors. The front door may provide more coverage as an entrance/exit, but then why stage the back door? The back door has nothing to provide it cover. It is a poor choice for anyone to pick as an ingress/egress. Of course it is possible that someone could have gone through the woods and accessed the trailer by parking their vehicle in another spot, then carried Haleigh all the way back to their vehicle, but we deal again with the visibility of getting out of that house. It is a great risk, and only a fool would take it, especially so close to the time when Ronald is known to be coming home.
For instance, Misty states she went to bed at 10-10:30. Give her the average 20 minutes to fall asleep, even 15 after the busy cleaning she had done up to that point, and the partying she'd be recovering from over the weekend before, and she's gonna be sleeping pretty hard. But 4 1/2 hours later, "she saw 3" and she was awake due to body functions of needing to go to the bathroom/get water. It is not improbable that someone waited until they saw the lights go off to make their move, so "just to be safe" waited another hour or so before going in. But then the staging makes no sense again. Why sit and wait, only to stage the door? Why not get in, get out and get gone? obviously in this theory, someone is at least watching what the patterns MIGHT be, but they can't know for sure. And they definitely don't know where the kids are sleeping. There would have been no way to know that until entrance (even if Misty took the blanket off the window, there would be no way a perp, sitting in the woods watching, could see UP into the trailer and DOWN onto the floor of the bedroom to the OTHER side of the bed to see where Haleigh was laying.)
So, this watcher in the woods waits, sees the bedroom light go off and is able to get into the trailer, traverse his/her way through the laundry on the floor, sneak into a squeaky-floored house, never rousing Jr or Misty and putting them on high alert that something was out of place (could happen; my granddaughter sleeps like a zombie) and goes right to where Haleigh is and takes her, still not waking Misty or Jr with the whole thing, impressively hoists the child up from the prone limp position of zombie sleep into their arms, back out the door of the bedroom, through the house and out.
Since Haleigh is in fact NOT in that MH by the time Ronald gets home, it is easy to see why people would conclude this must be what happened, instead of viewing all the components and being able to see why it most likely did NOT happen this way. As you state, Flossie, it doesn't shoot the theory down for you. Ok.
But not only does it shoot down the theory for me, it leaves only one theory that I can work with, and that is that something happened to Haleigh long before that 911 call was made and everything else was staged to make it appear as though she were snatched by a perp, known or unknown.