The 7.1 would not work as it is a matter of choosing which ISO track to use, and not all of them all the time (voices played) when editing with a 7.1 clip.
Until there is a better multitrack container style editing for editing, the Sync with Mix track is sort of a 80/20 solution meaning:
1. Import BWF with all tracks (MIX+ISO)
2. Sync with MIX track only. This “assumes” that this will be good for most of the editing.
3. When you get to a need for one of the ISO because it works better, match frame twice – once to bring back the sync clip, then audio only match frame again in the source monitor will bring up the original 8 track BWF at that point to use the ISO as needed.
Not as ideal as a dedicated multitrack container where you could make the edit, then right-click to bring up the ISO track desired for that edit. Maybe in the future.
Michael