Or merge Tempcode and Comcode, with the only difference being whether white-space is preserved or not (we currently informally call this "textcode"). So what are now Tempcode directives will just become new Comcode tags. Tempcode symbols can keep looking the same, but be called Comcode symbols. HTML would work natively in Comcode, as it would be like semihtml parsing mode is always on.
We could have an auto-decoded document-type that is 'normal' for a template and 'textcode' for where we now have Comcode. And invent 'textcode' and 'normal' tags to switch. Drop the existing 'semihtml' and 'html' tags.
So it is a combined HTML+Comcode+Tempcode language.

The term Tempcode would then be preserved only for the name of compiled Comcode.

Now that templates and Comcode pages are almost the same thing, we can add a 'Edit screen template' link on every page that is not a Comcode page, to add uniformality. We can merge the Comcode and template editors. We could even allow the template editing to be WYSIWYG on any individual template that is itself a valid XHTML snippet.

This simplifies the structure a lot. Now there is just one language, and any screen can be edited.

Closing, as the new inline WYSIWYG editing approaches this in a different way, makes it more visual. There's something nice about Comcode being like BBCode, and Tempcode being very grammatically simple so just slots in without distracting too much.