I agree with your theory, but an easier way to explain the relation between pattern buffers and your "Jjarro underpants" (heh heh, I love that...) would have to do with FTL communication.
Assuming Durandal had communicated with, or at least received communictations from the Pfhor os S'pht, he would have the capability to receive FTL communications. Now, since we can assume Durandal knew you were a JU enhanced cyborg, the other AI's probably found out, and possibly configured your JU to send out an (encrypted?) FTL message. This message would contain all of your memories since you activated the last pattern buffer (the PBs being outfitted with FTL receivers, in addition to being able to store patterns). Now, by activating a pattern buffer, let's say you set it to receive message's on your JU's frequency (and possibly upload the encryption key?). Now, when something goes FTL, it travels backwards in time, right? I know this is ovesimplification, but let's say at the time of death your JU send out your updated memories, wich travel back in time. The last PB you touched, which you set to receive, would get the memories, and as soon as you activated it to save for the first time, have the unsuccesful memories put into your head.
The overall effect would be the same (the environsments would "reset" each time you load a save, your physical body would be the same, etc.), but by incorporating the JUs, it almost solves the problem of why everyone isn't doing it. I know there are problems, (like almost all of MI, but that's kind of a grey area with the Wr' and all) but it seems to me like it could work.
I agree that Bungie probably just needed a quick way to explain the save feature, and I salute them for trying, and I'm noticing that most of the theories are similar in effect (ie once he dies JU uses quantum means to transmit memories back to PB, the marine uses time hop techniques to send memories back to PB, etc.), and the only thing still being debated seems to be the execution.....
