Handling multi complex multi cam audio

I'm after advice.
Up until now my multi cam edits have been of events where I have the audio from one trusted central microphone (Zoom) and all has been straight forward.
I recently videoed an outdoor wedding on a tiny island in a lake circled by the 'audience' in a forest on an island (Innish Beg) in Ireland and good audio is a all to be found but a minor nightmare to mix the various sources at the various times. Basically a multichannel mix is required. Oh to have each source on it's own physical fader. Can anyone advise the best way to extract the Multicam audios and work with them in FCP? I've found a way involving compound clips but feel I'm missing something. Is it time to start working with the audio in other software and if so what and I assume I will still need to extract the audios from the synchronised Multicam tracks to do this anyway? Any advice appreciated.