not sure I follow... you want to create a forum, but then not have any topics or posts in the forum? and have the forum redirect another page? if so, can you elaborate on the use case? not sure I understand why you would have a forum and then not be able to use it...
but probably multiple ways to accomplish if I am following...
one, just add a redirect to your .htaccess file... or use a wp redirection plugin that would allow you to do same for the forum url/page...
alternately, you could probably use one of our filters (standard wp filter) and replace the forum link url with your own... the hook would be 'sph_ForumIndexName' and then just replace the href of the a tag with your own url...
This feature is present internally ( or using a plugin) in quite all forum platforms such as phpbb, icyphoenix, bbpress etc.
The use cases are various and they can be similar of your current topic links. For example you can create a support forum adding a subforum called "contact us" that redirects to a contact form and that can be also seen directly in forum index.
As you said it's quite simple to implement it as an hook using filters. But would be nice to have it as core feature / plugin 🙂
Yes it shouldn't have any topics
However my suggestion would be to have a single entity called "Forum" that can have 3 different type:
* category / group
* Standard forum
* Forum link
in this way you can simplify managing, creating unlimited hierarchy also for groups and extends forum functionalities in future.
It's the way bbpress handle it.