The key problem with any/all of these theories is that Lucas seems to be on record with the notion that only Obi-Wan, Yoda and Anakin have ever managed to pull this trick off. And none of them happens to die in ROTS, which is Lucas's last chance to explain this to us.
So either Qui-Gon comes back and explains it, or one of these guys "discovers" it somehow during the course of ROTS. Either way, seems like we're in for a lot of clumsy exposition as something that should have been shown to us is instead told to us.
Much like Vader's own disappearance...never shown, but we're expected to just accept that it happened.
My suspicion is that this is not going to be adequately explained.