Abduction is inseperable from the McCanns because it's their theory. They suggested it and they have promoted it ever since. Would the authorities have decided that Madeleine was abducted if they had been left to investigate in peace? I very much doubt it. I think their attention would have turned to the parents much sooner than it did.
But it isn't only the McCanns who claim abduction - the Tapas 7 also do.
The idea that those people would risk the ruination of their own children's lives and put their own freedom in danger for a couple who some were not even friends with - let alone close friends - is way too far fetched for me. Normal decent people would never agree to get involved in such a heinous crime - and they are all normal decent people IMO.
I wouldn't do it and I don't know anyone who would in those circumstances - and I will never believe that Fiona Payne would encourage her own elderly mum to commit any crime - let alone one so serious that it could have resulted in her being arrested in a foreign country and being charged with attempting to pervert the course of justice! Not a chance in hell of her agreeing to put her at that risk IMO.
There was nothing to stop the PJ from investigating anything or anyone they wanted to - they were in charge. The reason they failed IMO is because there were no official guidelines for them to follow and because they took the investigation in the wrong direction once they decided to pin the crime on the mother - on the strength of a dream she'd had.