Newer cpus processing power increases over time, older cpus get cheaper over time, hard drives get bigger and cheaper over time, this means nodes can get better over time. Centralization risk is people not being able to afford onchain BTC and having to use custodians or shared custody of their funds. The risk is having a chain that only the wealthy can afford in a self custody way, because we want to be able to run Core in a raspi from 2018 over tor. And then while trying to find another way to solve an impossible problem we add complexity to the chain. People that can't own/use btc won't run nodes, people can also share a trusted node if they want while keeping their keys. We already had a big blocksize increase with segwit and there was no problems with the number of nodes. About fair fees, we could either increase blocksize in a dynamic way watching the median block fees for X blocks to assess if a blocksize cap increase would be done, like the hashrate adjustment, or it would be done always, like 1% every year, or it had to be hardcoded and in the future we would have to deal again.