Score following (listen to the attached MIDI keyboard and highlight the current score position)

There are programs that can open a MIDI file, generate musical notation from it, then 'listen' to the attached MIDI keyboard and highlight the current position in the score.

The fundamental flaw of these programs is that they generate notation from a MIDI file - this is an impossible task, because MIDI is not meant for this. So the generated notation is terrible. Example: Home Concert Xtreme.

There are other programs, they show correct notation and can follow the score. But you cannot open any file - you need to buy music pieces from their stores. It's not very expensive (usually $1 - $2 a piece), but most often they don't have the piece that you want, or they have the piece but you need a different arrangement of it. Example: Tonara.

If MuseScore had this feature, it would have a unique advantage over all this commercial software.

Or maybe you could make a commercial plug-in for this feature. I wouldn't mind paying for it. In addition to highlighting the current position, there may be additional educational features. It could check for correctness of pitches, timing, dynamics and so on. But I think that this is secondary. If Musescore could do what Tonara does, but with MusicXML - there would be a lot of happy users, even if this feature was commercial.