Constraints for email address

I would like to see a date constraint added to the email address field. my initial use-case was to automatically update unsubscribe or invalid email data to NULL based on an email address update, but there are probably more use cases that would be helpful. This data exists in SFDC, but there is not currently a way to query and apply automated workflows upon it in Marketo. I'm sure others would like to see different constraints as well, but currently I see date as making the largest impact for our Marketo instance.