As appealing as the flexibility is of the key path approach is, it's really a workaround for a missing language feature: the ability to nominate a differently-named function as the implementation of a protocol requirement.
This feature exists in underscored form as @_implements and has been used within the standard library in a couple of places in order to finalize the ABI. Ideally, this attribute could be productized and the underscore dropped. You would then write something like e.g.:
struct Person: Identifiable {
@_implements(Identifiable, id)
var socialSecurityNumber: String
var name: String
}
Given the potential of this feature, we shouldn't bake into the ABI a workaround that could have negative performance and usability implications for the long term.