A page management would be great, as we can add extra pages or even set up our own 4xx/5xx error pages. But it's an extension rather than a core feature, in my opinion. I suggest it can be made available as a plugin through API hooks. Suggested API hooks here looks like
add_menu_links
,
show_extra_page
or something.
However, I come across another idea that may cover this feature. Maybe in some feature version, we strip off some features that are really independent from core forum/post engine, like
page management
,
user promotion system
,
content type management
, etc., and group them into a set of pluggable features/modules/plugins that are provided and supported through MyBB. This design is popular among IM softwares (eg. WeChat, QQ) and CMS (eg. Drupal, WordPress). But it should require massively rewrite of MyBB. I hope in the future MyBB can do this.