I don't think you have this.. but if you do where is it?
Pretty much "customer fields", where users or customers could fill out information during registration that includes more to their profile. This would allow users to store extra information for user in the public (like facebook profile, twitter profile, etc) and for admins (Your product serial number/code).
You could make fields that users could only fill out once; after which it becomes a perm settings only admins could change. Maybe you only want to supply support for a user account with a specific serial number. By doing that you could setup a subscription possibly for them to their account on your website while making sure they don't change their code/serial number that is covered.
If you do a subscription upgrade, you could set the subscription package to upgrade to unlock specific fields for editing. This would allow you to purchase a custom field unlock, for new fields required and/or modification of previous field (code/serial number supported could be changed).
Just saying, that would be pretty great, but I feel like it might exist already somewhere? :S