On the issue of whether it's better to author HTML by WYSIWYG or by using a Poor Man's Hypertext, I tend to flip-flop. I've recently written Mimulus, which is one of the former, and am now working on Avocet, which is one of the latter.
But in thinking that I'd like yet another directory to take some quick notes in, I realised that it would be rather nice to macroise some of the pains of XHTML, and yet to do so in a way that preserves the XML well-formedness. In other words, a kind of variant of XHTML which can be converted to XHTML 1.0 using a stylesheet.
For example, it'd be nice to do this:
<doc title="This Will Also be the h1!"> <stylesheet href="style.css"/> <p>Hello there. This is an <a href="http://example.org/">example</a>.</p> <include ref="address"/> </doc>
It'd also enable one to use CDATA more freely, which would be rather a benefit when giving XML examples such as the one above! Perhaps the format could support CURIEs, too.
On conversion, it would become regular XHTML that can be validated with my xhtml.rnc, and it would be given a head/@profile so that the transformation could be two-way.
Another advantage is that the format itself could have a RELAX NG Compact schema, so it would be usable in nxml-mode.