- Introduce \DefineHyperURL and \UseHyperUrl to 
  allow definition of external URLs in the document
  preamble and usage at any position in the document
  so that redefinition of URLs become easier
  Add names \...ExternalURL?

- after reference text for ref pageref noref as optional parameter surrounded by (,)?
  (to be passed as 5th parameter to hyper@setref)

- Introduce Base Reference for External Links
    base_name: html:<base href = "href_string">

- Introduce corresponding Macro(s) for inserting
  relative links

- Introduce Other Link/Referencing mechanism
  that uses "type of stuff.number of stuff"
  instead of an internal code as an alternative.

- Consider the following part from html.sty (and allow additional optional parameter):
    %%% HYPERREF 
    % Suggested by Eric M. Carol <eric@ca.utoronto.utcc.enfm>
    % Similar to \ref but accepts conditional text. 
    % The first argument is HTML text which will become ``hyperized''
    % (underlined).
    % The second and third arguments are text which will appear only in the paper
    % version (DVI file), enclosing the fourth argument which is a reference to a label.
    %
    %e.g. \hyperref{using the tracer}{using the tracer (see Section}{)}{trace}
    % where there is a corresponding \label{trace}
    %
    \newcommand{\hyperref}[4]{#2\ref{#4}#3}

- Is it worth to develop a native PDF support?