After some consideration, and discussion with people handling "the paperwork"...
The place where requirements for automated tests is "best expressed" is in the statement of work (contract), where the items-to-be-delivered are identified. So, things like source, user guides, SDKs, etc., and...automated test code/scripts.
Which, of course, means that the requirements can focus on the performance requirements for the capability being contracted for.
This makes sense (to me), and keeps things "where they should be".
