It'd be great if S1 included the ability to share MIDI information across several MIDI tracks. A typical and common application would be layering. For instance I may have a MIDI track playing my bassline sending the notes to an external synth, but I also want to send that MIDI information to another MIDI track that has a sub-bass VSTI for instance. Right now I have to copy all MIDI clips from one track to another and every time I want to make a change I'll have to do that again.
Having the ability to select another MIDI track in the MIDI IN field of a MIDI track would be such a great feature I think.
EDIT: an alternative way would be the ability to add more than one MIDI out on a given MIDI track.