Hi Stéphane!
People have asked this before. I'm not sure about the arpeggiator, but about the sequencer, Philippe's answer has been that this is not currently possible, and it would be difficult to map the Origin's sequencer signals to MIDI, since they have been designed to work just like analog modular sequencers. I might make sense to use an external one like Beatstep Pro, and feed the MIDI into Origin and the analog CV into the Mg.
I will try doing MIDI out with the arpeggiator.