choral rehearsal tracks

I would like to see a new feature which creates rehearsal tracks for choral music. My definition of a rehearsal track emphasizes a single staff and de-emphasizes the other staves, this typically done via volume.

Ideally, the feature would allow the user to request creation of rehearsal tracks, which would produce a dialog with input to select the volume of the emphasized staff and the 'background' staves. Then, the feature would automatically create a file for each part which could be distributed to members of the chorus.

Some preliminary discussion of this idea occurred here:
https://musescore.org/en/node/278779

The mock-up by Daniel R is the right idea. Something more generic than SATB would be better, since it might be TTBB or some other variation.

The dialog might also need user input for the type of file produced: mp3, musicxml, etc.