How about the two volume knobs for OSC 1 and OSC 2 in the top center of the front panel
Yup, this.
Beyond that, in my humble opinion, the master volume should always be an instrument-level setting. The sound designer cannot know how the player has their DAW / mixer / interface gainstaged, and should not make assumptions about that by messing with relative volume levels of the instrument itself.
But in my opinion people work different and if it would be possible to realize to have the decision how it works it would be nice.
My Moog Voyager allows this and so there´s the possibility to have the mixer complete open and to regulate the volume by the volume-knob.
Or do you think there´s complete no difference, with which level you go into the filters ?
I looked up the Voyager manual to see how this was implemented. It lets you select whether the master and/or headphone levels stored with the preset are used when the preset is loaded or not, and lets you see this setting easily with the display. I would certainly be okay with that feature as long as I could turn it off, and as long as the synth had an easy way for me to see whether its off or on (like the Voyager does... it has a real display that clearly explain the settings). With the Rev4, we now have the third globals page which I consider precious real estate, and I hope the features that are added there are done with care and sparingly. That said, as long as this feature was turned off by default (and I didn't have to modify it again after every OS update etc) then I would have no objections to it.
I will say I think part of the magic of the Rev4 is its simplicity -- the lack of features guides the player toward focusing on the musicality of what they are doing rather than the technicality. I don't want to see it get cluttered with features so that it starts to feel like playing a Roland Fantom or other workstation (not that the Fantom is bad its just not what I want in a Prophet). Features like PolyUnison, being able to voice-limit the P10, and being able to switch between P5 voicing and round robin are killer features that bring something special to the synth. I can see the convenience factor of being able to store volume with the patch, but to me twisting the volume knob occasionally is just part of playing.
What I think would be interesting is if Dave came out with an add on hardware interface (sort of like the low frequency expander) that interfaces with the keyboard. It could have a real display and new controls that open up new capabilities for the synth. Maybe bi-timbrality, split mode, arp, sequencer, etc. It could be a platform for all of the various and sundry features people would like to have.