See this collection for code rules: Ineligible for Discount Code
Collection which contains all items that will be made to be ineligible for a discount code.
A daily job will run on Bulk Product Edit that will say that any product NOT in this collection will have the tag applied: Eligible-For-Discount-Code
A collection will exist for the criteria: Tag is - Eligible-For-Discount-Code
All discount codes will now only apply to the Eligible for discount code collection.
Another daily job will run on Bulk Product Edit that will say that if product contains tag Sale-Collection, then it will REMOVE tag Eligible-For-Discount-Code