BS6SC
It is quite possible that what interests Voldemort is not only Edmund's body as a "spare vessel", but also his soul. After all, this Voldemort seems devilishly more intelligent and "awakened" than in canon. He must have realized the debilitating effect of horcruxes. What if Edmund's true purpose was to "fix" his soul ? After all, their souls are supposed to be identical, right ? At least that would be true if Edmund wasn't reincarnated. :)
To my mind an option comes as plausible. It isn't that Voldermort want's a spare body and possess his younger body, there must be better ways to do that. Nor is it that he plans to merge with his young self or anything. To me, this is a plan around the prophecy. As it ties him and Harry being the ones to kill each other, he wants to try kill Harry like he always tried, but, in case he can't, he can have his younger self trying to kill Harry, since he would be trained to be so above Harry that it is a joke. In scenario 1, Voldy manages to kill Harry, so now himself and his younger self can just go on; In 2, he fails, and sends Edmund to kill Harry, since to his knowledge Edmund is just his younger self, he succeeds and the world goes on; In 3, Edmund fails to kill Harry and dies, oh well, a shame, but now the prophecy was fulfilled and Voldy can go on, with a few resources lost to Harry, but he tried at least. What really makes me wonder, is how and when Harry will sneak into the role to kill Voldy...
what if this leech on his soul is essential to his existence in this timeline? it's a very unlikely scenario but the thought doesn't leave my mind...we are all so aware of Voldemorts mindset to infer that he is sort of preparing Edmund to takeover his mind, body and magic in a sense.... but it's nagging me that Edmund is soon going to do something this this leech and end up regretting it....yeesh...