Sounds like you need to fork and start your own coin/chain. Bitcoin is not easy to change on the base protocol level, if there is any contention it will not be adopted, the idea of making backward breaking changes as you describe and introducing proof-of-stake is not a subtle change and has no chance of being pursued.
Isn't that what Bit Green (
https://bitg.org/) basically did to start? Now they are trying to have more of a positive impact rather than simply reduce energy use (in part as they realize there are many low energy use alternatives to bitcoin including Cardano and Nano to name just a few). FWIW, Nano is in many ways the peer to peer cashless network described by Satoshi. Of course, the bitcoin community has been able to create a much larger market cap by brining in 3rd parties and repositioning btc as a store of value.