Would this work?
Assign whichever channels to Grp 1&2 creating a mix. Pan Grp 1&2 hard Left and assign to Mix 5&6. This effectively gets sent mono out of the left side of Mix 5&6.
Create another mix using Grp 3&4 and pan hard Right. Assign to Mix 5&6 and this will be sent out of Mix 6 (the right side of Mix 5&6)
Essentially,
Grp 1&2>Mix 5
Grp 3&4>Mix 6
Grp 5&6>Mix 7
Grp 7&8>Mix 8
Matrix 1&2>Mix 9
Matrix 3&4>Mix 10
Yes, you sacrifice sub groups and matrices BUT if you need to supply a separate mix to 10 people on stage this seems like the way to do it.
I’m going to try this later today unless someone first explains why this wouldn’t work…cheers!