Much like the pattern variations, it would be great to have a variations menu in the arrangement track. When an arrangement really works for a project, I would love to be able to save it, then when starting a new song, the arranger track could have a load button were you can instantly recall your saved arrangements from past projects.
As a song writer, I usually have 8-10 different arrangements I stick with, it would be nice to have them saved as arrangement variations in the arranger track.