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We can't blame people if why they are doing the HODL scheme. It is because of the loopholes that the current bitcoin system have even if it is giving benefits to most of the users.
I may agree that the percentage of bitcoin being used in illegal activities are much lesser than before, yet I am still pretty sure that the black market might be using other cryptocurrencies.
Also, your idea might be just impossible to achieve, because decentralization is possible thanks to trustlesness. So, to make your system work, you somehow have to find a way to trustlessly measure all the costs of Bitcoin mining operations.
It is actually possible as long as the developers can make something to solve this equation. Mind that all the transactions are being calculated and by collecting all the data we can actually measure the costs of every mining operations. Then possibly the devs could create a system for it. Tho this idea is like digging a hole on the rocks using your hands.