You can create a mesh with the first frame, this will be the "source mesh". You can then create many linked meshes from that and rename each for the next frames. When the linked meshes have Inherit deform checked, they will get the same deform as the source mesh. Now you can animate the deform of the source mesh and also key the slot attachment changes to get the frame-by-frame animation for that mesh.
Generally deform keys should be avoided because they must store a lot of data, especially for a weighted mesh. Another way to do it is the same as the above, but use bones and mesh weights to deform the mesh rather than deform keys. This is both more efficient and easier to animate.
