Well, the simple problem you've raised could be solved by a library of portlets. Then you, the person who puts up a site, could provide a suite of portlets that the user can choose from to customize their own page.
Portal support in OpenACS 3.2.5 is very primitive. In ACS Classic 3.4, it was improved somewhat - this is what aD's Oracle-based ACES is based on and ACES takes an approach very much like the one I outlined above. In ACS 4.x Classic, portal support is considerably better. This has already been ported into the OpenACS 4.x framework.
Providing interesting portlets that interface to existing packages could be a fun way for someone to contribute code if they don't have the time or inclination to develop an entire new package.
Portlets are self-contained. Having a library of portlets would make available a lot of the building blocks needed to lash together the kind of "vertical application" packages discussed in other threads.
