Thanks for starting this thread, Anyhoo. Lately I have come to see this type of theory as the one that answers most of the forensic evidence, as well as the motive, and the circumstantial evidence.
FWIW, I do believe BR was a very, very troubled child and do not doubt that he was abused within the family and perhaps by close friends. Add the invalidated reports of him displaying symptoms of aspergers, and I see most of the witnessed behaviors after JB's death being very believable without having to suspect he was involved in anything related to it short of learning about it very, very early that morning when he asked questions during the 911 call.
Support of a JR molestation/PR catching them in the act:
1. Chronic vaginal evidence at autopsy. Statistics declare an adult male most responsible in child sexual abuse. (I have to add here that I believe JAR and even Burke were also involved with JB...she was trained by PR to believe sexualization at her age was acceptable. I believe Patsy grew up that way as a victim in her home, and accepted her adult lifestyle as a sort of "reward" that was a complex mix of daddy worship, love of money and beauty, and secretive behavior.)
2. The "secret Santa visit" expected by JB, with the Santa suit, admittedly JR's, taken into evidence by BPD. Cotton was also taken into evidence, which I believe prompted questioning of JR later by LE with regard to the type of material the Santa beard was made of. The angel ornament taken into evidence from the WC also connects to JR: he called JB his angel when he laid down on the floor next to her after she was placed in the living room. JB had a tree in her room with angels on it, one especially for Beth, and that JR recalled in one of his books that he had been using medication to help with his inordinate continued grieving for Beth that year. I have always wondered if the angel ornament was the one representing Beth that might have been taken from JB's tree and carried along on the trip to the basement.
3. The photo posted up on FFJ some time back with what appears to be a "Holiday Barbie" from that year packaged as a gift, in a somewhat disheveled display. JR disclosed in one of his books that he had wrapped Christmas gifts himself that year....and I believe the Holiday Barbie could have been used as an enticement for JB.
4. The time of the death as determined from the digestion of the pineapple would match up well with the supposition that PR could have fallen asleep while finishing some last minute packing activities, but awakened to recall the need to take JB to the bathroom, only to discover her missing from bed. And after checking the other bedrooms and also seeing JR gone from bed, went quietly about following up her suspicions of molestation.....grabbing the flashlight and keeping the lights off to remain undetected by JR as she set about the search.
5. Patsy was suffering from fatigue, use of alcohol, reported use of anti-depressants, and as much as she downplayed her ovarian cancer, I believe she harbored a real terror of that cancer coming back at any time. It is a killer cancer, and that deep rooted gnawing at her along with the physical hormonal changes coupled with LHP's report of the trouble in the Ramsey's sex life, could have produced a bubbling volcano of rage just waiting for the spark that would ignite the explosion.
6. The RN screams PR. Try as I might in pinning that on JR (and I have really tried) I must conclude for myself that the RN was part of a quickly concocted scheme to develop something that looked as if an intruder came into their home and killed JB. JR might have had some input as to how to "reason" the plot, but I believe Patsy put the plan together, only to then become the one to place the 911 call which disrupted the full plan which would have allowed for removal of her body because she could not bear to dispose of JB into the elements. I think she transitioned into becoming a genuine basket case as the effects of her rage wore off. She had to live with her lie, but without her daughter in the beginning it was horrific for her.
7. The plans for Charlevoix and the Disney cruise indicate to me that her death was not premeditated prior to the head blow. All indications were that the family had plans which would have taken them all away from Boulder and into each other's close company for a good deal of time, and that supports the idea that JR would have additional reasoning in his mind for a special sexual event with JB for Christmas.
8. A scream by JB could have been accounted for by pain OR terror of seeing her mother coming at her in rage with a raised weapon poised for the blow. The type of head injury indicated force with intent to do harm much more than a knee-jerk reaction by JR to pain JB might have caused him. It's also possible the scream came from PR as a reaction to her discovery. If JB's scream was a reaction to pain caused by JR, he could have stifled her (with some kind of short choke hold?) as she struggled until he could put his hand on a weapon that he could use intentionally, fearing she would have that time disclosed the truth.
9. JR's shirt fibers inside her size 12 panties lead me to believe he was there with her at some time after she returned from the Whites and before she was brought up from the WC, when she would have been without any sort of bottoms at all. One pair would have been off in order for the size 12's to go on.
10. I believe the pineapple and tea were prepared by Patsy and Burke, and that JB was a part of snack time. It is at this time that Patsy could have then decided to go off and do some packing, or even head for bed, thinking JR would or could get the kids to bed. Maybe BR was next to bed, with JR planning to save "bedtime" for JB for last. Could he have actually taken her to her room, put her down, and returned very shortly for the secret Santa visit? Pretty easy for him then to lead her down to the basement, accounting for the lint found on the bottom of her feet.
It is possible the molestation attempt began gently in her bedroom, but it was planned for escalation which required the trip to the basement. Given the condition of the train room, and marks on JB that could have resulted with her body coming in contact with the track pieces, I suspect somehow there could have been havoc related to the molestation occurring in the train room, possibly complicated by PR's discovery of them there. I believe the WC was the "dumping" spot for things they could not dispose of or try to return to their original spots that were related to the crime and any staging that happened. Naturally, some things would have been overlooked in the aftermath...other pieces of paintbrush left in the tray, the pineapple snack not cleaned up. So much to do and so little time before early AM and the ruse would have to ensue.
I believe the ligature was used by JR, but constructed by PR. It is not a stretch to me to think that he told PR they should put a garrote device around her neck to make her death look like an intruder killing, especially if they felt they might actually have to end her life because she was not gone from the head blow. PR could have collected up some of her supplies from her art work, gotten the cord ready, but had to hand it off to JR for the final deed if she could not go through with it. He was the one most likely to be familiar with garroting being used as a quick method of debilitation, having been stationed in Subic Bay, where the garrote was (and still is) a major method of debilitation, crime and death. He had to take a shower and clean himself up, and with PR still wearing her party clothing from the night before, this might have allowed time for her to fashion the ligature and write the note. JR would have needed time to make sure all forensic evidence related to being close to JB sexually, and perhaps even in a struggle, would have been thoroughly cleansed and then disposed of.
The reveal of the GJ indictment placing responsibility for JB's death on both parents has helped me to finalize my decision of a sexual molestation related crime involving JR with JB, and PR acting out against JB in rage upon full awareness of her participation with JR. I believe PR was keeping a blind eye to what she did not want to accept but probably suspected for a good deal of time about JB involved incestuously not only with her son, but her husband, but then the perfect storm of that Christmas became the stage for what ended up being the "Perfect Murder, Perfect Town".