Idea: m-theory gets developed earlier.
M theory has some wierd ideas. 11 dimensions, various membranes, etc.
It also says that if one were to view the known universe from a membrane, one would see the entirety of time and space (maybe even the whole quantum divergence of futures thing).
It also says that gravity acts on our universe from another brane entirely!
Imagine the near-omnipotence of such weapons!
Is something a weapon if it nullifies a threat without killing, capturing or discomfitting the origin of that threat?
What if you could pick a target, then fire something at him that would reach back in time and modify his appetites such that he would be happy where he is and want nothing more?
What if you could stop someone from trying to kill or conquer you by making him the happiest guy in the world?
Oie! ...Or just nullify his existence so that he never was.
Also... what happens when multiple people look into the quantum future and the vision takes into account the peering of others?