If this is indeed by design I am very suprised by what I think is a glaring oversight of an elegant way to compose in the score (selecting articulations with MIDI channels).
The Vienna Instrument player appears to be bountiful in ways of selecting articulations, especially suited for real time performances, but composing with the proverbial quill and paper it doesn't seem to offer an elegant method of selecting articulations (without cluttering the score with keyswitches).
As an AU/VST plugin that may be used 'within' a sequencer, it seems odd in this day and age that it is not multitimbral, especially when offering such a robust Matrix, along with a myriad of other ways for selecting articulations.
Will selecting articulations by MIDI channel ever be implemented in Vienna Instruments?