Oh I know the political implications of changing BTC are high, but the main arguments against changing anything to do with Bitcoin are its security profile. I agree that BTC is the most secure chain. But, if the mining reward dries up to the extent that it is less secure as transaction fees take dominance, then the community will have to sacrifice one of their sacred cows: 21 million supply or proof-of-work. Neither one of those are easy to change, but if necessary, it will have to.