This should be useful (and would be likely to link in with the prototype that @deepmap-marcinr has been looking at) to allow users to modify a spec that ie they don't control, prior to generation

For instance, for the ability to tune the generated output, when you don't have control over the spec

See also: https://docs.bump.sh/guides/openapi/augmenting-generated-openapi/ and pb33f/libopenapi#125