thank you graphite,
I agree that miner rewards is a potential problem in the future. If transaction fees don't go up the blockchain will be vulnerable. I like the Idea for compressing the blockchain by getting old UTXO's to be used but I still don't think this would be the right way to go.
higher transaction fee will benefit classic banking systems and approves the benefits of their cross-border CBDCs. so this is not a good idea.
I think a better idea would be instead of halving the block subsidy every 4 years it should flatline at 1.5625BTC. This would insure miners will keep getting rewards and keep securing the network regardless if transaction fees increase. This level of inflation should be negligible. only 82,125BTC will be mined each year which is only a 0.39% yearly inflation rate.
putting such inflation on btc is against its whitepaper, but adding new fee structure could pass by a BIP, I think.