[binarybanana]

But what if you had a spinning black hole to play with? Couldn't you strategically place a bunch of satellites in various orbits around it and use the frame dragging effects in either direction to manipulate signals into arriving arrive somewhere else at arbitrary times by sending them around often enough?

I can think of two ways in which one would still be limited though. First is that one is limited to dragging signals only as far back as when the necessary machinery was first put in place. This is analog to the limitation of the wormhole time travel hack where you accelerate one close to c, then slow it back down and put it in place again to increase the distance in time to the other end that was stationary the whole time. But perhaps even worse would be the hard limits on how much this could be used before the whole apparatus itself turns into a black hole by the sheer energy being sent back from the far future. it would be like a time lense effectively. Or less spectacularly, it might just get fried. Or perhaps a failsafe would just dump the signal before things get critical. In any case, there would be a limit to how much or from how far in the future one could use such a thing, but other than that it should work, right?