Well, I am going to wait and see what these alleged "lying" charges are about.
There is definitely some confusion (from the media articles) about what they might relate to.
Nothing stacks up - as far as I can see - that there was enough time for a domestic death and a coverup that was so good that it has lasted all these years. imo
No theory about this case stacks up for me.
If we go with abduction then we have a scenario where someone who was inclined to take a child just happened to be in the area at the right time. This, I can see. But it still has some unlikely elements to it because this is a cul-de-sac in a suburban country area. More significantly, however, we have the fact that FM says William was only out of her sight for about 5 minutes, maybe less. Kids can move quickly, but in my view that leaves him within viewing distance of the house and other houses in a fairly open area. Would a child sex offender who was not there for the purpose of nabbing William, take the risk of grabbing him when the parents could have actually seen him or anyone else could? Was there even time for it to happen - for the urge to be developed, for an instinctive plan to develop, for him to take William and be out of the area before FM saw him? I just simply can't see that happening.
If it's two people, how did they collude in this time?
I understand why Jubelin/the investigation became obsessed with the neighbour and washing machine repair guy (I know their names; I'm not going to use them because I think that's unfair). I don't agree with it, mind you. But it makes more sense that it was someone who had a specific reason to be there and was comfortable in the street because that does away with having so much being left to chance - better means and opportunity. I cannot imagine there is someone else who fits this category who wouldn't be a POI. So, given that is not an option, we go back to the random scenario.
The only way I can make a random scenario fit is if William was actually out of FM's sight for longer than she has said, whether because she simply doesn't have a clear idea of time or because she was worried about the consequences of saying he was gone for, say, 20 minutes. This gives him time to get much further away, perhaps where it is obvious he is not near his family, and somewhere less visible. It also gives a bit more time for someone to make the decision to take him.
I can understand the initial commentary that it was only 5 minutes, but I have never understood zealously sticking to it, whatever the original reason. If it was me, I'd be saying, "Look it could have been longer" even if I didn't think it was longer just to broaden the options of what may have happened, and because I would never trust that I could be so accurate about the time under those circumstances. To me the difference between 5 and even 15 minutes is significant here. That is not, BTW, a suggestion of guilt about anything.