The ability to filter by the first value held of a property

In addtion to the many contact property filters that already exist, such as:
contains any of
is known
has ever been equal to any of
updated in last

etc…
it would be a great to be able to filter by the first value held for situations where a property value changes over time and you want to know the original value of a property for a list of contacts.
A use case for this would be:
Problem: The various forms on our website, such as the ones for our ebooks, demos, pdfs, tools, etc., update a contact property called “Source” through the API. Since each time the property updates it overwrites the previous, there’s no way to see the conversion rates of a list of contacts who originate from a specific source. For example, “has ever been equal to any of” doesn’t exclusively show the original property value.
Solution: The ability to filter by the first value held of their source property would give insights into the lead’s origin, and help answer questions such as, "What is the conversion rate of contacts who originate from this specific source?