If you are saying that the Web Controls should be replaced with XSLT I agree whole heartedly. This has the effect of moving the HTML out of code and into a stylesheet.
In this case replacing is really removing since the main function of the Web Controls is to produce the HTML. If you have the content XML then XSLT can be used instead of binding to a Web Control. I use ASP.Net without Web Controls.
I don't really see what you are referring to as the facade layer - perhaps System.Web.UI.Control - but in most cases it wouldn't make sense to get XML from it. For instance the XML for a checkbox or a textbox is fairly useless; it's the XML for the content
that is going to be used in the checkbox or textbox that is useful. This content XML would be provided by another layer that is completely separate from the Web Control.