I was thinking about the practical aspect of using an Alcubierre drive, assuming one existed.
I'm no expert, but my understanding is that, since the destination has to be in the forward light-cone of the vehicle, there is necessarily a preparation phase.
For example, if you wanted to travel 100 ly in a year, you would set up the drive, point it the right way, let it "warm up" for 99 years, hit the switch, and get to the 100 ly destination in 1 year of subjective time, but the whole process still took 100 years.
Would the payload have to be on board during the 99-year warm-up period in this example? If so would that payload have to be causally disconnected from the region of spacetime which doesn't make the journey? If so doesn't that imply that the destination couldn't receive a FTL response to a message it sent to the vehicle, since the equipment on board wouldn't be able to respond in less time than it takes the drive to warm up?