Sorry, coming in late catching up to Emails.

Regarding what Dries said, it seems we need a form registry
whether mandatory (declaratory/explicit) or deduced (implicit).

We seem to already have one that Heine wrote, Form Store:
http://drupal.org/project/form_store

There is also Form Corral
http://drupal.org/project/formcorral

These may be good starting points ...