The hier part of the guide is meant to provide the source for the porthier.7 man page. It doesn't right now, but we are intending to base all manpages on the guide very shortly, so changing the guide is how to get the man pages changed. Right now the guide has the most up-to-date information because of this pending new way.
It would be nice.
I'm not really qualified to comment on the technical merits of your proposal. But I'd be happy to look over what you've written for style and format if it passes approval by our base developers.
The main advantage I hope this guideline would bring to MacPorts is consistency. No one wants to be in an inconsistent filesystem. Unfortunately MacPorts filesystem is not so good at this point. Let's say I just installed mysql5 and apache2. Where's the configuration files? for mysq5, It's located in ${prefix}/etc/mysql5 by default. for apache2 ${prefix}/apache2/conf/ by default. Where's the log files? mysql5 uses /opt/local/var/db/mysql5 apache2 uses /opt/local/apache2/logs/ Who can say MacPorts' filesystem is consistent? If MacPorts had a strict hier guideline and the project recommended port developer to follow that guide, every conf would be in ${prefix}/etc/${name}/, logs in ${prefix}/var/logs/${name}. It's so clear and easy to remember where to look at when I need it. I believe this would improve MacPorts's usability so much.