Good work around, unfortunately, it seems to be mac only. My work around is using a midi keyboard on a single note/hold/arpeggiator so that the midi note sent to the expression maps is simply repeated super fast.
This has the bonus feature of If I want to make on the spot legato ensembles or staccato tuttis, I simply need to hit the legato or staccato relative key on the keyboard and then ctrl-select the multiple instruments and they all switch to the same articulation. Your maps need to be standardized to do so but it works pretty well.
Last but not least is filtering the midi notes at the input so that out of range notes of each instruments do not end up in the piano roll hen I play wide chords on an all brass of strings ensemble. That way I can record a piccolo and a double bass simultaneously for exemple without my left hand recording silent midi notes in the piccolo’s midi event and vise versa.
I still can’t select pizzicato on the bass and legato on the piccolo with the my technique unless I stop the arpeggiator and then I get the same issue so we still need a fix for this midi channel reset on stop. Is there an alternative to Keyboard Maestro on Windows?