You have a deep misunderstanding. The source of decentralization in Bitcoin is the market (economic incentive structure) not the devices. If you cannot afford expensive hardware then let that go because the people who can afford expensive hardware will mine. People with the most money will always have the best hardware from which to mine. Mining is always for "rich people" who can afford to burn money to support the security of the network.

If you are worried about centralization around hash power then that ultimately happens no matter what strategy you use if it's Proof of Work. You could let everyone mine on CPUs and eventually it centralizes around pools and farms, You could let everyone mine on whatever physical devices you want and the fact that it is a physical device is centralizing. Only the economic incentives control how centralized or decentralized it is, in my opinion.

Core in my opinion has the incentives wrong. For instance Craig Wright endorses unlimited forks (decentralizing), larger blocks (which could lead to a higher price as a side effect), if Bitcoin becomes more valuable (again economics) then the cost of hardware isn't an issue unless you want every user to also be a miner which doesn't make any sense or have any impact on security that I can see.

If every user is a miner or not, the security in my opinion isn't going to scale based on how many individual persons are mining with their smart watches. Diminishing returns in my opinion there, but hey I could be wrong.

Tell me why I'm wrong?