Implementation of hook_submissionapi

I know this issue have been discussed before, but I want to take it another round. As addressed in http://drupal.org/node/368723 it's possible to hook the webform submission process with other functions and modules using form_alter, but it would be much cleaner to provide some api hooks to integrate other modules. My suggestion is to create a hook_submissionapi where other modules could provide actions and manipulation on different events in submission creation.

It would be pretty simple to implement, and in my opinion the right path to go making webform more useful as a Drupal module.