I've been a longtime Premiere user, but hadn't needed to delve deeper into Multicam sequences until a project I started today. I spent all morning and ran into the same limitation you described. Now that I've discovered a solution, I've been posting replies to all the threads that have had this issue, so someone searching for the solution like I did this morning may see it too!
Using screenshots and putting text together using Photoshop, you can view my workaround here:
The first step is creating your Multi-Cam sequence properly:
The second step is duplicating the multi-cam sequence's audio onto separate tracks, then enabling Multi-Camera on the audio. You then switch each audio to the corresponding track number.
Hopefully that makes more sense in the image:
It's not perfect by any means, and it's a little messy, but it'll get the job done. For me, it was a necessity as I am cutting scenes and may need to mute the boom track, adjust levels on a lav track, etc.
I hope my diagrams make sense; I sorta cobbled them together quick because I really wanted to share it with the Adobe community before heading back to work!
Toggle only track 1 in the multicam sequence and then check Audio Follows Video.
Thanks for the reply. Will try this when I next get some footage to sync up. I've tried it quickly with 3 random files but couldn't get it to work. I may have missed something since I sped through it though.