I'd much prefer that the OutputTransform pipeline not expose the stage ordering. That probably means that we should have a way to send any injected HTML through "all stages prior to the present one", especially for pluggable pipeline stages. For example, when a skin inserts HTML for section edit links, that HTML might have localization messages etc and so it should be sent through "earlier stages in the pipeline" to ensure it is expanded; if you added hooks for extensions to add new pipeline passes they should get a similar API so that their exact placement in the pipeline is not exposed, etc.