Change Instrument via plugin

I'm trying to create a plugin to transpose scores for different instruments in an automated way. I'm quite aware of the various ways of manually invoking the "Select Instrument" dialog in MuseScore (via Add/Text/Change Instrument, via the Text/Change Instrument palette, etc.). However, it would be very useful if this function was exposed through the plugin API. That is, a function that would simply take an instrument name in text format (or as an id from instruments.xml) and do exactly what is done when the "Select Instrument" dialog is invoked.