Specifically, I want to be able to work with forms without having to know anything about them. I'd like to see us add some semantic metadata to them. Some of this metadata should be (i) human- readable, some of it should be (ii) machine-readable and (iii) some of it should be both.
Indeed that would be the first catch to make writing a clean UI for the action configuration. However - the action would need further information about the form such as a list of available form elements, so that the action can alter them. So we either need more metadata describing the form elements (puh..) or the action has to simulate executing drupal_get_form, which would require knowledge about the needed arguments. As jeff said, tough... Anyway, a neat idea! -fago