It'd be worth trying running the sequencer in Hold mode (via the software), with the oscillator waves turned down to 0, and getting that constant retriggering of the envelope that way. I'll need to experiment with it, but you ought to be able to process input signal that way to interesting effect.
If you'd rather not use the Gate routing for any reason, then if you connect a MIDI controller with sustain control (e.g. sustain pedal plugged in to it) and activate that while playing a note, that will keep the signal coming thru.
Otherwise, you'd need to manually retrigger the keyboard any time you wanted the envelope to reactivate, maybe with a long release setting if you don't want to lose sound in between retriggers. Even with the small form factor, there's a lot of possibilities.