Both rests and ties would be incredibly awesome and would make the arpeggiator 1000 times more useful and more like a true sequencer (it is already very cool anyway, but this would be beyond cool). Unfortunately I suspect the only mechanism buttons we have available to do something like this would be the octave +/- buttons and the tap tempo button.... not very much to work with, and I think the tap tempo button already does something special if held down.
Maybe it could work this way?
HOLD DOWN Tap Tempo and simultaneously press Octave Down for rest, or Octave Up for tie (where a tie would just sustain the same note for the consecutive beat, or multiple beats depending on how many times you insert ties
this way you could hold notes out for longer durations)
I don't think that would interfere with the current "hold tap tempo button" functionality (which I believe affects what the tempo does when you hold the button and turn the tempo knob).
Going a step further, maybe that tap tempo button could just be turned into a "function" button that does different things depending on what mode you are in.
If ARP SEQUENCER MODE is enabled AND the unit is currently switched to "HOLD" mode: Hold Tap Tempo and press Octave Down or Octave Up to insert Rest or Tie (if Tie is entered after a Rest, it would insert another rest).
If sequencer mode is NOT enabled (i.e., set to factory standard), then when in "HOLD" mode maybe use this method to allow us to toggle whether the ARP re-triggers instantly when you play the keyboard or stays on its own steady beat and just changes the notes.
If ARP is set to "On" mode, could then allow this to set different options pertinent to THAT mode (not sure what...)
And then if ARP is "Off", could use the Tap Tempo + Octave Up/Down to enable/toggle two other specific features that might be helpful.
Probably crazy to try and implement all of that... but sure would be nice!