Paul,
I did something similar to this, in my case I wanted studio program audio (coming from our Dante side of the FR12) to be routed to the cameras in each of the studios in question. The objective was to put program audio on each camera to be used as an ISO without the need to dynamically route each time I wanted an ISO.
I would create a source labeled with a mnemonic that speaks to you of its combined audio nature.
Then in that source I would go into each of the audio channels and manually update those entries. As you can see below my studio c camera 1 takes video from that input but replaces the first and second audio channels from Dante aux. Continuing along this way and modifying audios 3/4, 5/6 & etc until you have your payload configured as you like. The only drawback i see is that there is no truly 'obvious' way to see this audio shuffling, you kind of need to know it it being done or you need to pay close attention to the table. The other thing is that the source shuffling appears to depend on the exact string (i.e don't change case, spacing or characters).
I hesitate to say this is the 'best method' for accomlishing what you ask but it is 'a method' that works in my use case.
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Chris Spacone
Broadcast Engineer
USC / ASG
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