Using previous alternate email as apple id
According to Apple's support page: 


Go to My Apple ID, click "Manage your Apple ID," and sign in.
Delete the alternate email that you have. Click Yes when it asks for confirmation.
With the Name, ID, and Email Address drawer selected, click Edit next to Apple ID and Primary Email Address.
Enter your new email address.


I just applied the following steps above to my own Apple ID and it did not complain.