Wormholes, nice move. Apparently the Great Minds of the 20th Century (And Beyond) agree with you . . .
"At that time wormholes were not something that were part of science fiction. They became part of science fiction as a result of this interaction between Carl [Sagan] and me [Kip Thorne]. . . .
(Narrator) With wormholes on center stage, Thorne soon found they had other mysterious properties. They could be used for more than traveling great distances in space; they might also be used for time travel.
(Kip Thorne) If you have a wormhole, then you can turn them into time machines for going backward in time. We thought, how could we have been so stupid? We should have realized that. It's obvious. . . .
. . .
There are several different ways to turn a wormhole into a time machine if you are a clever and infinitely advanced civilization. By an infinitely advanced civilization I mean, somebody who can do anything their heart desires except they can't violate the fundamental laws."
--excerpt from an amazing PBS documentary circa 1999, wherein a "discussion" is had between the likes of Kip Thorne, Carl Sagan, Stephen Hawking, John Wheeler, Igor Novikov, and David Deutsch -- all geniuses with their own theories on the scope and possibilities of Time Travel.