The "others" who are "worried" about the energy cost of Proof-of-Work aren't sufficiently educated enough to understand Proof-of-Work, or they're just enemies of the ecosystem. We all know how Proof-of-Stake works, and if there were no tradeoffs compared to Proof-of-Work, we'd have already switched to it. But, it comes with some serious disadvantages, those are centralization and security sacrifice.

Anyway, if your idea requires no consensus, as I've already said, it can be built as a sidechain.