We’re open to experimenting with this in core. The ‘flash’ of differently-styled content can be a little disconcerting, so we’d like to start with it behind a default-disabled “experimental” site setting to start with. That way, Site admins can choose to enable it if they want to.
Are you able to try adding a site setting in your PR @rrit? It would also be good to add some RSpec tests to verify the behaviour with the setting enabled / disabled.