Active Mixer in Playback
In theory, the nuances of performance are encoded in the dynamics, articulations, expressions, etc., but in practice, there are adjustments that can more easily applied via the mixer to achieve more effective playback. Ideally, I would like to see the ability to record changes in mixer settings along with the score for subsequent playback. I do recognize, however, that real-time tracking of this data is probably not possible at this time within the design of MuseScore.
As an alternative, I would like to suggest the possibility of inserting "mixer snapshots" into a score via a place-marker such as Staff- or System Text. The framework for such a function could be similar to the existing Instrument Change text, or applying mixer channels for sound groups. eg. arco and mute for strings. These could be applied either globally, or to individual instruments. We can already save instruments settings mid-score; why then, can we not do the same pan settings or other playback tweaks?