In todays wordpress, i can have only "pages" and "posts". It would be great, if there could be an option, or prepared "background for plugin", for making a special type of "page" - which would basicaly use the same table, same columns, just different "type", so it will not show with list-pages / post functions, it will have own functions (it should be universal, where the desired type would be a parameter), it would be easy to "switch off" the unnecessary parts of the "add page" page, add new fields (saved as meta), and you could define, what will be shown in the "manage pages" table. And it would be possible to define user rights (add/show/change/delete...) to any type
This functions is crucial for many applications, e.g. you could then easily do a "shop" - just use new "page" type as a database of shop items, or for any other site-specific content and is one of two reasons (+ user groups), why it is necessary to use other systems sometimes.
This is i believe quite easy to do, as most hooks and database structure is prepared.