> Unfortunately, that means that attempts by those larger providers to combat spam using such reputation will naturally hurt smaller providers
Tin-foil hat time, but I've always thought there was nothing unintentional or "unfortunate" (from Google's perspective) about this.
While there's some truth to that, neither SPF nor DKIM nor DMARC have anything at all to do with reputation.
They serve to authenticate that the sender is somewhat connected to the person who controls that sending domain.