Preventing users from removing a contacts email address on the request

I have been running into an issue where my contacts were randomly being duplicated and the original contact would no longer have an email address. I was able to track down the source of this issue being that when a request is being entered/edited if a user removes the contacts email it permanently edits the contact record. The issue here is that i need the users to have this edit permission but i need to prevent them from removing the emails when the request is being modified. Is there any way that i can accomplish this?

Also, is there any way to easily reconcile these contacts? There are potentially 297 contacts with this issue(probably less but it is currently my best guess without further analysis).