Counterweights are already a pretty common thing for existing VR headsets. Some people will strap a battery pack to the back strap of their headsets, and there's enough tethered players looking for plain counterweights that's there's a small cottage industry around custom made heavy metal counterweights.

Here's the one that I bought to use with my "frankenquest" (Vive Deluxe Audio Strap on a Quest 2) setup: https://www.studioformcreative.com/product-page/vive-das-200...