The ORTC CG is making great progress on many fronts and it looks like the conversation around RTPSenders & Receivers (formerly known as Doohickeys) is taking more shape in the WebRTC WG. They even have a name there now: RTCRTPSenders / Receivers. The WebRTC WG teleconference call today was far less controversial than I am used to, it felt like everyone is trying harder to get things done.
I am not convinced we need Constraints at all in 1.0, by the rumblings on the calls it seems as though I am not alone. You can see that conversation taking shape in the Working Group here: