It would be useful to specify a default slug for system pages.
Currently, the slug is auto-generated from the page id, which is often OK, but sometimes the page id will be named to include e.g. the extension's name.
So for instance, a pagetype with id "ems_my_events_page" would be given a slug of "ems-my-events-page". While this can be edited, very often it will not be, and can lead to ugly URLs!
In this case, we might add to the page type definition: