Hello,
This is a good idea and not a use case we had considered before. We will look into adding this to the near-term road map. If this is a requirement for you in the immediate term, please send me an email and we can discuss what we can do for you.
For now, what some of our customers do when they want to set limits on particular outbound streams is set timer events when they receive outStreamCreated events. Timers (and other API calls) can receive user defined variables allowing you to store additional information which will be sent back when the timer is triggered.
Bryan