Maybe I'm confused, on this request but the Pattern Editor is only sending MIDI "type" data, so note on/off's, controller information, etc. Any instrument connected to the Pattern Editor is where the overall Volume and Pan would have to exist. For instance, if I have the Pattern Editor controlling U-he's Diva, how would the Pattern Editor tell Diva to control pan per lane per step? It could transmit MIDI CC10 maybe but I don't think very many instruments respond to that as per-voice pan. And for volume, if you had one-shot samples loaded up in your instrument, velocity will control volume. If you didn't, then again, most instruments are not going to have separate per-voice volume in addition to velocity.
I think you need to look at the Pattern Editor as an extension of the PRV. We don't have per note volume and pan controls on the PRV. But, it would totally make sense for an instrument to have those controls. Hope that makes sense. Otherwise, maybe I just misunderstood this request.