Bulletproofs, rings, privacy, all that could be done on a sidechain in the Monero way, the software stuff. But Monero people would still claim Asic reliance in the Bitcoin that backs it is a weakeness.
A future Asic supply chain or hash capture would mean capture of both Bitcoin and the Monero sidechain. Capture in the sense of censoring or disabling the sidechain, not breaking privacy.
RandomX solves a real threat that can't be replicated in a sidechain as described in bip300/1. Anyone can support the Monero network with a basic cpu. They would need an asic to support the Monero sidechain(Bitcoin)