Managing value sets

Summary:

Right now if you disable or end date a value from a value set, the objects where that value was assigned show blank in the related attribute.

What should you do if you don't want this data to disappear, but you want to prevent users from assigning it to any new objects? (And you still want to search for all the objects with that value)

Sometimes a historical value contains valuable information that may be kept for some time, even if it is no longer relevant and should not be assigned to anything else going forward.

Agile had an elegant way of handling this - are there any options for Product Development?