Thanks for the timely reply. In some uses I think the shortcodes idea is a good one, and I saw that option here and in the docs. But my usage in this case is creating restrictions, based on extended roles, on bbpress forums (where the entire page is locked down and there is not really any content on it to wrap in the shortcode).
In multiple bbpress forums, I use Enabled role permissions to allow for specific sets of members to access specific forums. From what I can see, it would be significantly more difficult (if even possible) to do so with the shortcodes.
I guess I can create a custom 404 page which includes some widgets and manual redirect links and a registration form to go with the search and other items already there. I can make it work somehow, I just thought the custom redirect would be a nice solution (but I have an admittedly limited understanding of the specifics of the plugin workings).
Thanks for your feedback.