Firstly, if one includes Martha Tabram (Turner) as the first victim, what appears to be a significant pattern emerges.
Martha's movements are fairly well known in the hours before her death. And without going into it all, it is highly likely that the murderer was not her last client with whom she was seen in public. In all likelihood, the murderer took advantage of an opportunistic encounter.
That supposition, along with the MO being underdeveloped compared to the other crimes, could indicate that the murderer wasn't actually posing as a john, but rather someone who knew the movements and habits of these kinds of sex workers and so took opportunistic advantage of them and their specific vulnerabilities.
Following on, Poly Nichols was found in a quiet, but exposed street, Bucks Row. Her injuries were far more extensive and horrific, but now more reflective of what was to follow. Annie Chapman, too, in Hanbury Street was even more secluded, though no less risky.
Liz Stride, in Dutfield's Yard again, risky but secluded. And even more so, Cathy Eddowes in Mitre Square. That location allowed a gloomy spot for unseen crimes.
Then, ultimately Mary Jane Kelly was indoors, the only instance of such in the series, of either the five or the six. Though it should be acknowledged that Martha Tabram was found on a stairwell landing, not on the street.
My instincts tell me that the murderer may well have been more opportunistic than first thought. I think the perpetrator may well have observed these women taking the risky action of taking a client to a secluded place, at which time he intervened to deadly effect.
Secondly, I think there is an escalation and development of the MO to seek more secluded places to facilitate the infliction of post mortem wounds which seems to have been the goal.
The implication of this is that all the eyewitness testimony of people supposedly seen in the company of a victim shortly before their discovery may well be useless.
The major flaw in this, is that none of the victims were reported to have had evidence of congress when examined. That said, there are other explanations for this which do not preclude the completion of some kind of transaction between the victims and their clients.
Another implication is that it increases the likelihood that the murderer had some kind of a relationship with Mary Jane Kelly. Hence the cessation in the immediately recognisable pattern.