We can certainly improve the Drupal front-end code to have similar functionality as the BOINC web code: Have the admin chose what kind of deletion to use: A or B. And even let the user chose between the two options: C = let user choose A or B. Option D could be 'no deletion'. Likewise admins may disable the boincuser_delete module.
I would prefer that the delete user functionality be controlled using Drupal and its admin interface, otherwise we will have too many near-duplicated config settings that will be confusing, even for ourselves in the future. Thus the Drupal module can be enabled/disabled, the admin may choose what type of deletion to run (or let the user decide), etc.
This can all be introduced in another JIRA ticket.