I disagree

For uniqueness you either need to agree on a centralized authority like ICANN.

OR

Achieve global consensus by adding it to the Bitcoin blockchain. But to me, that seems expensive and unattainable for most people in the future.

I don't like either of the former solutions. I think accepting that no globally unique owner of [short name].nostr and building for that is more realistic. You can give a name weight by putting PoW towards it or by social consensus, which is how the world has operated since forever and it works quite wel... If I say 'London', you probably know what I'm talking about and which coordinates it belongs to, despite there being multiple London's out there