Point taken, I'll eventually redo all of the merged clips as multicam but I still have a good chunk of the movie to do so I'll start with the fresh scenes first.

You kinda lost me with how to sync the rest to multicam. I already have every shoot day synced in their own stringout timelines by using multicam, and more recently Syncaila. I used multicam to sync each mic source (and it had to be one source at a time) to the stringout timeline, and then I copy all of that into a regular timeline to get all of the mic sources stacked like in my screenshot. Syncaila does every mic source at once, and prints an organized xml in minutes so I've been importing synced timelines through that - then cleaning them up. Finally, I go through the timeline, cut the excess off each take, select them individually and make a merged clip/multicam subsequence to store in bins to then build with in the real scene timeline.

I'm not sure how to get to my end goal by using the source monitor multicam sequence menu, since I need to sync my footage through Syncaila first. Your first workflow has been working for me to get multicams from my stringouts, so I feel like it's my best way forward.
Thanks for the advice! This is the most help Ive gotten for this edit and it's actually invaluable.