Reverting avatar & signature fields upon subscription expiration

[stwilson]

I understand how permissions work in combination with the paid subscriptions but have not been able to find a way to automatically remove extra permissions granted by the paid subscription when the user does not edit their account. Here is my example:

Registered user:
Membership: Registered
Signature field - 100 characters
Avatar - pick from library

Paid subscription:
Membership: VIP
Signature field - 200 characters
Avatar - pick from second library or upload

When the subscription expires, the user account has the following:
Membership: Registered
Signature field - 200 characters entered when the user was a VIP member
Avatar - from second library or uploaded when the user was a VIP member

If the user never updates their avatar or signature they can keep the paid subscription level for those profile fields. Is there a MOD out there to purge these settings automatically back to the level prior to the subscription or to just blank them? If not, can someone recommend a query for me to blank the signature field and null out the avatar field?