The nonce-calculations are what makes bitcoin an energy credit. It's why it's a valuable digital asset and commodity. If it cost ZERO dollars to create bitcoin it would just be fiat... useless inflation adding zero value to current shareholders.

Bitcoin are being traded by energy companies to subsidize their infrastructure and improve energy efficiency and capacity.

In some ways Bitcoin is a battery, because hydro dams don't idle generators as often they can sell their excess energy production and subsidize the dry season. Oil companies capture the natural gas flares and use it to power generators to mine bitcoin, etc. There really only needs to be one POW coin, and I think it's pretty obvious that Bitcoin is it.

because all that will do is just entrench the existing banking oligopoly.

proof of work is the only thing that maintains unforgeable costliness.

Every proof of stake system eventually centralized and failed.

What about proof-of-space?

And of course proof-of-work isn't necessarily immune to wealth centralization either.

PoW is far from immune to it as the Chinese have proven, as they hold roughly 49% of all BTC and 65% of all mining capacity on the planet.