Is it possible to use sfz sound fonts or even Kontakt instruments with PianoBooster? I would like to use more realistic sounds with PianoBooster due to its accompaniment feature. I'm planning on using PianoBooster during public performances and I think that would help open-source and free programs gain popularity in my community, but I need to use more realistic sounds than sf2 instruments. Thanks.
It should in theory already be possible to use PB with sfz as PB works well with any external program that provides a midi connection. You might also need to use some sort of midi bridge to connect them together if the PB midi output device selection does not work.
Sorry there are no plans to integrate sfz soundfonts or Kontakt instruments with PB as fluidsynth is the only integration that PB will support internally and fluidsynth has no plans to extend to different file formats.
You could try the MuseScore_General_Full SoundFont which has improved instrument sounds.