I've been making backing tracks for myself from downloaded wav stems. In those stems there are few instrument tracks that are 2 beats off compared to the rest. It would be great (and expected) that I could just move those tracks in place but I don't think that's even possible atm.
So I would suggest adding the option to move those tracks IN show page. I can of course do a song, fix the problem there, bounce those tracks back and add them into the show. But if you have for exapmle 20 songs you need to do, it's gonna add up a lot.