This has probably been mentioned before but I haven't come across it in reading old posts here.
The one thing that makes sense to me regarding the railing and lack of smudging/dust/dirt removal. What if RZ never went over that railing? Could the killer(s?) have had her in the kill room taped to the chair, looking on her computer/cell phone VM/etc., writing on the door, preparing to kill her, and somehow RZ escaped? She runs through the house and out to the courtyard. She screams as the killer(s?) catch(es?) up to her, hits her in the head, drags her over by the balcony, and does a "reverse" hanging? Maybe one killer in the courtyard, and one in the kill room?
To me it explains her muddy feet, yet no mud in the house, the wounds on her back, but not on her arms, and the miminal disturbance to the dirt/dust on the railing. If one killer threw the rope up and over the balcony, the other was there to catch it and tie it to the bed, it could have rubbed back and forth across the railing a bit. It might also explain why her feet were only a couple feet off the ground instead of many. There would be no need for such exact measuring of the rope if she were nealing (hog tied) on the table, the rope goes up, gets tied off to the bed, and then the leg gets kicked out from under the table. The rope connecting her legs and arms gets cut after the hanging. Kicking the table out from under her could have caused the bed to move at that time.
Probably 1000 holes in my theory, but it just doesn't make sense that she went over that railing in any fashion, at least to me.