As for a body double appearing after you turn the wheel. Very good possibility but I think Locke will be the only double. It may be a result of the Casimir Effect and his exposure to electromagnetic property in The Swan.

http://www.youtube.com/watch?v=4bTvAUVPyLI&feature=related

^ Every should watch this video.

i see two possibilities.

1) richard and the others get rid of the bodies (like they were concerned with during dharma time).

2) MIB/nemesis inhabits the dead body which is why you don’t find the bodies later on. The reason that locke’s body is seen is because turning the frozen wheel causes the turner to not only appear in tunisia (but also creates a body double (read about tesla’s invention in the movie The Prestige)

to add to number 2…
locke was told he had to die because MIB didn’t want him getting in the way… there is no real “has to die”. it was part of a long con.

The doubled body on island was killed or taken over by MIB, which is why the extra body exists in the case that Illana brings.

We will find out that ben’s body was also doubled in season 6.

He was neither dead or on the island at the time so we really do not know how the rules apply.

Illana is clearly on a quest as she marches the body from ‘Jacob’s’ cabin (where she thought MIB was … and he would have been ‘cept oh powerful ring-of-dust* was broken.

About the body – since SHE had the original Locked-box, the bodies DO reach the island and are not directly necessary for the transformation/Flocking.

BUT … *maybe the impenatrable ring-of-dust is made of the body’s ashes and somehow makes that person trapped ‘within himself’. If so, it would probably be Locke who broke the cabin’s ring and how he helped the Hyporcrite (e.g. fake Christian) within. (i.e. Locke took the Hypocritic Oath in the cabin).