The problems that can appear is the way how we will make the emittor moves so fast for example: having not enough space in the laboratory. And the second problem might be how we will slow it down due to not cose a collision of the scatterer and the source. One of the solutions to the first problem can be putting on one fast train the scatter and on another train, moving in the opposite direction, the source. Then we could achieve the same effect when both trains would move with the same speed which is half of the speed of sound. It also partly solves the second problem.