There are many times when optional repeating blocks in requests have a corresponding number of responses. It's unwieldy (or sometimes impossible) to provide contextually-correct responses when the number of blocks in the request changes.
Obviously, it's best to use CA TDM to accomplish this and output the required data into running virtual services, and failing that, Data-Driven Virtual Services should be investigated in DevTest Portal. In this blog entry, I discuss an approach within DevTest Workstation to provide this facility.