Restrict cloning and copying transactions

Using classic custom fields in some tabs like (Sales Invoice) for a long time, This new year we decided to use the new custom fields and deactivate the classic fields just in case @lubos abandon the classic feature at any time.
The problem is when a user clones or copies a transaction We can’t edit or delete the stored values in classic fields.
We have three ideas here:

  1. Restrict cloning and copying transactions for some users (User Permissions).
  2. Restrict cloning “inactive custom” fields while cloning or copying transactions.
  3. New option to replace the classic fields with new custom fields and merge both.

Sure, the developer can resolve the problem with another idea.