Hi!
I think a song mode would greatly dawn in a new style of music. I say this as it has some very unique features & being limited by 5 tracks makes arranging within the unit a special journey /a force of style.
A basic song mode
Each Song Step carries
- Number of Repeat
- Track # Patterns
- Part Mute/ (on/off settings)
- Motion sensor position
this allows the user to sculpt a large arrangement out of just a few patterns or reach very rich and complex arrangements with many pattern if willed
Some sequence setting information would also be very exotic (if viable) per song step (like clock, start/ end etc.) although one could recall this with patterns its always super nice to experiment things out in song mode.
Other Song Mode features
Hold song step = when you dont want to jump to the next transition quite yet and just jamm on current pattern
Forward = when you want to continue from hold
Im not going to post to many suggestion as I dont have a unit (and dont know its structure/flow), but song mode is very big for me personally and it’s a zen like experience to compose with a tactical interface that is simple yet quick/ effective and always super fun … so much faster/insperational vs a DAW
I will add though that it be very nice to be able to recall all touch sensors '‘sound’’ via Shift + Corner button
a kind of scene recall state for the sounds … this is often quite handy when you are playing live; you’re into some feedback high reso jorney with the club walls about to come down… yhea that moment in the set where you are about go off the cliff, all the way into a ‘‘WTF look’’ on one of the dancers face and quickly want to revert to a ‘‘safe state’’ 
Think Elektrons have this as a feature, on my Spectralis it was a case of triggering the same pattern again to revert to the original state. Don’t know if it’s the same with the PP, but this would at allow the user to have 4 sound scenes on recall if he so required
Thx!