Since you asked: what are your thoughts, Mack The Knife?
I feel sort of inconclusive on JS still. Since LE has not named JS has a POI or suspect or anything, and the only charges right now are against SS, the information that is public is obviously directed at the investigation of SS, so I don't feel like we know all that much about JS, really. I think I'm more skeptical of statement and body language analysis than the general consensus of WS users, so certain things that have been red flags for a lot of folks with JS ("we" dropped her off, referring to MS in the past tense, etc.), haven't bothered me as much. I'm leaning toward, right now, there is no significant evidence (known or unknown) that JS was criminally involved in the murder of MS or the attempted cover up.
I feel a bit more confident about my general theory of the case. That is built primarily on the big doc dump because that is what I read most recently and there is a lot in there, less so on the early interviews and press conferences which I haven't watched since they happened, some general absorption of what has been shared here, and not at all on other videos/reporting (like from Court TV or Gray Hughes) because I just don't like watching videos.
Pure speculation alert...
My leading hypothesis: I actually don't think SS is a pedophile. From what we know or have heard about his other preferences and habits, I think he is more of a generic deviant--I don't want to go too deep into this area because it's more just a feeling I have, but there is a path wherein people addicted to p-rnography get numb to "normal" stuff and seek things that are increasingly extreme and end up with CSAM, and I think something similar may be the case for SS. That was more than I wanted to say on that but I think it's relevant because I don't think that MS was going to age out of SS's preferences, as could happen when a pedophile's victim goes through puberty.
I don't think MS told anyone about her abuse. It's not unusual for victims of CSA to not tell anyone or to care for their abusers, which it seems like she did. I couldn't guess how she thought about it or internalized it, but to me it seems like no one in her life had any inkling. Maybe JS had an inkling, I don't know. Maybe if she didn't, she should have. I don't think MS told her, and I definitely don't think SS thought JS knew.
In this hypothesis, SS was at a lot of points lucky and a lot of points brazen. I think he intended to assault/abuse MS on the first night he was back in town, and because he hadn't been around as much in the prior few months,I d something somehow was different and went wrong--maybe MS pushed back--and he regained "control" of the situation by killing her. He then scrambled for how to cover it up, and landed on her going missing some time after he drops her off at school, which included the absurd idea of putting her body in the front seat of his car.
I don't think he ever really assembled a full plan of what he was going to do because he was probably freaking out. I don't think he's some cold-blooded killer, I think he's a coward and killed her out of cowardice. And finally, his luck ran out and his brazen moves caught up to him because he was repeatedly caught on camera moving a dead body, his story was easily falsified, and he gave police consent to search a device he kept CSAM on.
For the JS aspect of this hypothesis, her knowing or being involved just doesn't fit.