I was wonder what people do in this situation.You have an admin area of a system where you let users define a list of values they want to see in a dropdowns across the system.What do you do in your application is a user wants to delete this option?What do you do with data records which already use this value?
Deleting Lookup Item
programming practices
One option is to implement a no longer in use flag.  Existing records remain the same (& the value continues to be visible where it was used), but it's no longer available as an option on the dropdowns.