new device that'll be automatically activated at first time it gets internet connection
I agree, but this is not exactly what I meant.
We need to differentiate between
a) Activation of new devices
b) Re-activation of existing devices
While I was talking about (b), you seem to mean (a). This is also possible, but to be completely honest, it may turn out to be a huge security issue. Let's assume a user can download a file, which grants access to his licenses on the server. If this file is leaked to the public, unauthorized users can activate their devices at the expense of the license's owner. It will be quite difficult to revoke that file later on, as it would prevent legitimate users from activating already purchased devices. The file can be encrypted/protected by a password, but in this case it still requires user interaction during the setup wizard.
I like the general idea and we would implement it if there is a secure way for unattended activations.