emphasize 1 voice in 2-staves (2 instruments) SABT / TTBB scores

Hi,
I couldn't find a way to emphasize (for playback, learning) 1 voice in 2-staves (2 instruments) TTBB scores for male choir.
We have a lot of such, actually written in capella, but MuseScore 2.x imports these fine.
(I found the https://github.com/Jojo-Schmitz/VoiceCaster -- just a js file. But if I put it into my Plugins folder, it does not show up, neither I'm sure it still should work with MuseScore 2.2., nor whether it is meant for my purpose.)

Is it possible to keep the 4 voices in 2 staves, but give them different instruments and volume each?
Each voice, one of Tenor 1/2, Bass 1/2, should hear its part emphasized by special instrument, but still the others in the background with reduced base volume.
At the end I'd like to get 4 learning mp3 files (1 per voice) from each mscz.

I would not mind to script something to manipulate the xml if MuseScore would support such mode, like 4 instruments in 2 staves.
What do you propose?

Tom