I think the parents statement today is very significant. It's obvious all the LE statements are well planned and it is apparent the family are listening to their advice as to timing of the releases and the content, to get maximum benefit to the investigation.
Despite all the other theories and possibilities, it still seems all the signals point to someone who she knew. While it's always possible it could be a stranger murder, and they should have a team looking at that angle, I think the vast proportion of resources needs to still be on those that she knew. While the circle of her acquiantences is undoubtedly large, by this point they would (should) have been tabulated, prioritized, and their alibi's checked and double checked. In today's day and age, alibi's can take the form not only of statements by others as to your whereabouts but also mobile phone signals, other electronic fingerprints (i.e. online activities) and CCTV. I am guessing that list could have up to 200-300 people on it. It would have GR, MW, CJ, PS, LORP, others in 42 and 44, everyone at BDP including those at the party, clients and contractors of BDP, all the facebook friends, anyone she had been in touch with based on phone and electronic records, former boyfriends, everyone at the rowing club, etc. By process of elimination many of those can be checked off that list on the basis of the quality of their alibi's. Those that have multiple lines of evidence of an alibi (i.e. witness account as to whereabouts plus CCTV) would have better quality alibi's than those that only have a single witness account. Not all witness accounts should be equally weighted - for example 3 people saying he was with us is better than 1 person saying he was with me (i.e. and he arrived at 10pm as far as I recall but I had 4 pints earlier in the evening, for example).
Although the time of death and location have yet to be conclusively established, the 840-920pm time frame appears to the the window of opportunity. 840pm being the end of the phone call with Rebecca, and 920pm being the time of the unanswered text. I simply don't believe that text would have been unanswered if the events that were to lead to JY's death were not already underway, regardless of how useless with her phone she was believed to be.
Isn't this also the day the "big clue" was supposed to be realized (speculated to be results of newer DNA testing)? Maybe that is not going to be the smoking gun they were hoping for and they are now realizing they are at a real risk of this becoming a cold case unless they can shake one of these alibi's from those remaining on the list. I think LE need to get through that list, forget about motive for the minute and only look at opportunity, and come up with a revised list that includes those with no valid alibi, or a shaky alibi. Is that where they now are?
A revised list of those with no alibi or a shaky alibi (i.e. single person account), would have to include GR, MW, CJ, PS and LORP, no? Any others?