It would be great to have a way of templating content, so that for any new page the web editor enters information into some controls on a form, and the entered values (which might include images) are rendered as html when not editing.
The required ingredients for this are (as it seems to me!):

1. data template (e.g. could be an xsd)
2. method of creating/editing data template (e.g. could be freetext editor with validation)
3. presentation template (e.g. could be html with data attributes defining which data element hydrates each html element)
4. method of creating/editing presentation template (e.g. could be freetext editor)
5. Auto-creation of data entry controls from data template (there are existing open source libraries for this)
6. Method of previewing the rendered result while editing
7. Caching of rendered html to help performance, busted on changed data values or templates.

It would be most powerful if data entered through content templates became queryable "data" rather than just shaped html.