The way I would do it is assign each microphone to different aux groups. Aux 1 will go to hall 1, Aux 2 to Hall 2.
So don’t use the master output, but the aux/mix groups instead.
Using aux outs would work or assign the channels to subgroups as needed and send the sub group outputs to the needed locations. Un-assign those channels from any other mixes.
Build up scenes with various routing configurations.