I'm not making a CMS perse, but more of an application framework, in which all functionality is provided by module controllers and widgets. And that includes static HTML.
So where a 'real' CMS is focused on admin pages where you would define the HTML (like in Pyro), here you would define your page structure, and you would say "on this particular page, in this particular section of the theme template, I have a widget that contains static HTML)". You can then navigate to the defined page, and if sufficient rights, edit the HTML inline.
You can see an example of this at http://exitecms8.exitecms.org (old version built on CI).