The shot is of clothes moving through the air in slow motion, as if they were being tossed from a suitcase.

Basically, I want to achieve steady focus on the clothes, panning with them as they move, the background will be a fast moving blur no doubt.

Is there an easier way to achieve this without physically throwing the clothes and trying to capture them moving in real time, then slowing it down in post?

Clothes on clear monofilament fishing line running through small pully... Large fan blowing...
Pull on fishing line to move... you can also drop them let gravity work for you and turn your camera sideways. just a couple of thoughts.