While I won't go even close to the PHP internals list, deciding on the community representatives will be... interesting. Drupal, which http://w3techs.com/technologies/details/cm-drupal/all/all powers 2% of the web has an army of subsystem http://cgit.drupalcode.org/drupal/tree/core/MAINTAINERS.txt maintainers. If you open the gates, whom of them will be allowed to and who won't? Fascinating.

Generally the idea is to give the head of the project a vote.

Agreed. I think I still have a vote, and I haven't been involved in PHP for about 6 years.