A Life on Mars finalé theory

I’ve interacted with a few Life on Mars fans over at the IMDB. Psyche-8, as (s)he calls him- or herself, came up with the following theory. It is far more complex than what writer Matthew Graham envisaged, but I prefer it to the “suicide is the way out” idea.
   Incidentally, I do not think I am spoiling this for our American friends. I believe that when David Kelley remakes Life on Mars, he will almost certainly have a different ending. It would be too easy for American fans of the new show to go to Google and read the finalé to the original.
   Psyche’s explanation actually makes more sense to me and solves the whole Sam Williams issue.

Right, I’m going to offer my two pennies worth to this debate and perhaps help to explain a few details. Here goes:

There are two Sams. One is a 37 year old man living in 1973 called Sam Williams. The other is a 37 year old man living in 2006 called Sam Tyler. 
   Both Sams have a great deal in common, so much so that you could say that they are living parallel lives albeit 33 years apart. There also bear an uncanny resemblance to one another. 
   DCI Sam Williams is a forward-thinking officer at Hyde police station in Manchester in 1973. When he was 12, he was involved in a coach crash which claimed the lives of both his parents and left him in a catatonic state for a while. He recovered, grew up and joined the police force. At the age of 37, he was offered the chance to go undercover as a DI, working to bring down the corrupt DCI Gene Hunt. He collaborated with his mentor, DCI Frank Morgan to come up with an alternate identity as Sam Tyler, a name he took from a grave stone near where his (Sam Williams’s) parents were buried, and he set off on his assignment.
   DCI Sam Tyler is a forward-thinking officer for Greater Manchester police in 2006. When he was 12, he was involved in a coach crash where he was injured but no-one else was seriously hurt. He recovered, grew up and joined the police force. At the age of 37, he was in the midst of a difficult case that he felt powerless to solve, and which culminated in the kidnapping of his girlfriend. Hating feeling so helpless, Sam found himself wishing that he could be somewhere where he could really make a difference.
   On the same day, at the same time, in the same place, exactly 33 years apart, both Sams were knocked down by a car. Sam Williams was killed instantly but Sam Tyler survived and ended up in a coma. However, because in that instant the separate timelines somehow overlapped, Sam Tyler’s spirit was transported across time and he woke up in Sam Williams’s body in 1973. Because of the fortunate coincidence of Sam Tyler’s name and Sam Williams’s assumed name, Sam Tyler from 2006 was able to seamlessly assume Sam Williams’s whole identity. Frank Morgan merely assumed that Sam Williams had successfully convinced everyone that he was Sam Tyler, little realising the truth and simply putting his strange behaviour down to amnesia from the crash. In the scene when he’s showing Sam the graves and telling him about his real existence as Sam Williams, there’s a very good reason why Sam has no memory of any of these events – because he’s a different person.
   However, while Sam Tyler’s body lay in a coma he was caught between the two timelines, hearing sounds and voices from 2006. He remained in this limbo-like state for a year and then finally woke up. When he did, he realised that he had a choice – to remain in 2006 or to return to 1973 where he could really make a difference. Because of the existence of Sam Williams in 1973, Sam Tyler had a ‘doorway’ to the past. He could go back, be Sam Williams for the rest of his life and no-one would be any the wiser. Thus, that was the choice he made and he knew that the only way he could go back and stay in 1973 permanently was to sever all links with 2006. Which is why he committed suicide. The body of Sam Tyler will eventually die. When that happens, Sam will be free. He'll stop hearing voices and be fully in 1973.
   So, what do you think? Good explanation?

   There’s a tinge of The Man Who Haunted Himself (the old Roger Moore movie) here.

PS.: Psyche-8 is a girl.