A number of synthesizers I've owned or used (such as the Elektron SIDstation) have a built-in arpeggiator which has a mode where it will only be active if more than one note is being played - for example, while playing just a single note it acts like a normal monophonic synthesizer, but as soon as multiple notes are held, the arpeggiator turns on and it alternates between the notes of the chord.
I would like to replicate this effect with Logic's arpeggiator module, so that I can make use of this mode of operation with any of my softsynths.
I have tried using the scripter module to generate this behavior, but in order to control the arpeggiator in this way it would have to be able to emit control change messages - but the arpeggiator does not have a control change that corresponds to being on or off, nor can they affect things like the arpeggiator length or the like.
Fader events also don't seem to be able to control the state of the arpeggiator itself, nor does scripter seem to be able to affect plugin state (it can only seemingly modify MIDI events).
In some limited circumstances I can fake this mode of operation by simply setting the note length to 101% and setting the synthesizer module to legato mode, but that has a bunch of limitations (for example, the notes end up getting quantized/delayed to the arpeggiator rate) and doesn't always work in the general case (for example it tends to fail if I have two chords immediately following one another more quickly than the note length), and furthermore, not all of the synthesizer modules I want to control even have a legato mode.
Is there a means of getting what I want, or an alternate arpeggiator effect for Logic that would provide this functionality?