Now to some of the details (This is rather for LaTeX inclined

> > * latex-output seems even less usable.

This is actually an understatement:

Currently, an inline node with a class unknown to the latex writer like::

  <inline classes="keyword">
            def

is converted to a function::

  \docutilsroleNone{def}

which is not defined in the preamble and hence leads to an error if the
documents is translated to PDF.

IMO, the missing feature is a "failsave" handling of class information:

  In HTML, the semantic syntax markup can be simply stored in a class
  argument to a <span> element. It can be used by the CSS stylesheet for
  syntax highlight and is simply ignored if no CSS rule for the given
  class exists.

LaTeX does not have a "class" attribute, so some emulation of this
concept is needed. Maybe we can use a \newcommand with optional argument?