Different SoundFonts are more suited for different styles/genres/periods, and so it is completely arbitrary to choose just one for every produced audio. As an example, Soni Musicae is built specifically for early music. A non-exhaustive list of soundfonts and their specialization can be found on the MuseScore Forums.
It could be possible to have $wgScoreSoundfont take in a dictionary, with an interface name that would be used as the argument, and its path for the fluidsynth or timidity command.
(Originally reported on fr.wiki.)