He mentioned it toward the end, but did not describe the solution. I'm thinking the counterweight on the other end would need to move a very precise distance in effectively zero time.

EDIT: hmm, or a supplemental weight on the payload side, moving outward the right distance as the payload releases.

It seems like you'd generally want the non-payload rotating bits to vastly outmass the payload, so its release perturbs the whole system to the least amount possible. And then you use regenerative braking to reclaim the energy .