[Vibraphon]

Perhaps I missed a change somewhere?

Doesn't MSP only require the song titles to match on the master and slave devices?
Thus, if the master opens their version of 'SONG XYZ' and it's in C,  the slave tablet would open 'SONG XYZ' even if that version is in Bb (unless the title on the slave actually included Bb). ...

That doesn't really work.
The sax player has a sopran, an alto and a tenor sax. So he uses sheets for the same song in C, Bb and Eb.
He cannot not name three different sheets the same.

I do see how your protocol could be helpful if someone were managing all the tablets for the whole band.

That would be a great benefit.
Every musician could use mobilesheets individually for different orchestras.
To manage all tablets it would only be necessary to define the exchange list.