I'd like to define my own models by extending the classes in account.models. For example, I'd like to provide my own EmailConfirmation model so I can override the send method to do some project specific things with the email templates. Have I overlooked something, or is this currently not possible with django-user-accounts?
Here's one potential way to do it using get_model().
Projects can create their own class with account.EmailConfirmation as the superclass and override what ever methods they need. Then define the new class in the settings file using:
ACCOUNT_EMAIL_CONFIRMATION_MODEL = 'my_app.MyEmailConfirmation'
Overriding models is simply not something supported. This is largely due to Django not providing a mechanism for handling that.
However, you are not out of luck. Recently we added the ability to use hooks to customize email template functionality. See http://django-user-accounts.readthedocs.org/en/latest/settings.html#account-hookset