As I see it, the existing ArrangerTrack is sorely lacking the ability to include lead-ins and fade-outs for song sections.
In detail: let's say there's a lead guitar playing underneath the chorus of my song. The chorus starts on bar 32 and ends on bar 48, but the last note of the lead guitar doesn't end until bar 50 because it's fading out for two measures. Right now, if I designate bars 32 to 48 as the chorus, and use the ArrangerTrack to create copies or move the chorus around: any of those copies or moved choruses will be missing the fade out from bars 49 and 50.
Suggested fix: create an option to allow users to link entire clips to specific ArrangerTrack sections to include any lead-ins or fade-outs. So in the above scenario, any time I copied or moved the chorus, I'd also be automatically making copies of (or moving) the guitar fading out for two bars at the end of the chorus. The same should be true if there was a lead-in or build-up going into the chorus.