Thank you, great suggestions.
One idea I had that I really wished I had enough time to implement was to create some future autoplaced notes that you can't remove. Like, at this place there will be a piano note in 3 loops, then you have to adjust what you're doing in order for that note to make sense in the run.
There were other ideas as well, like regions where you could not put some instruments or regions that you get bonus points if you placed certain instrument...
But unfortunately I didn't have time to do all of that.