im planning on composing some lot tunes for my front ensemble my senior year, and having a marimba would complete the ensemble mostly. there vibes, Xylo, rack and kit percussion, but no marimba. i think its a great instrument to have anyways.
New instruments are unlikely to be added as we don't really need new instruments in the first place. Just focus on using the instruments that are currently available or switch to a DAW that has support for such instruments.
Musescore is a much better option for composing music to be played by a band. It should have all the instruments you need
