Your idea of creating the yyy-stream is the EXACT right way to do it. The other options are decent workarounds for one-off situations, but creating the extra stream is simple and is fully leveraging AccuRev's capabilities. That being said, I understand that your admins have stream creation locked down. They of course want control, but should be allowing for maximizing developer productivity and not forcing workarounds like this. My guess is they have stream creation locked down to a particular group being enforced by the server-admin trigger. One common thing I have seen other large sites do is: - allow streams to be freely created off of a list of acceptable streams (easy to do in the trigger) - enforce naming rules on the stream creation. This is important to admins in large sites to keep things organized. Again, this is very easy to enforce via the server-admin trigger.
Bottom line, if this is a common situation, work with the admins to allow this capability as per the above. If they have any questions, they are more than welcome to contact AccuRev and we will help them out.