To improve both the editing and displaying experience of SharePoint WCM Publishing pages I would like to be able to switch to a special set of Masterpage/PageLayout when in edit
The definitive answer to this question is now "baked" into a product which we call DualLayout for SharePoint! Our approach solves all your SharePoint WCM design nightmare:
Check it out at http://www.macaw.nl/Het+Bedrijf/Producten/Macaw+DualLayout+for+SharePoint.aspx, see the blog posts in the blog roll of that page for detailed background information.