Remote speakers usually require an independent mix due to the imbalance from the lack of direct sound from the stage. As such, take advantage of a matrix for the remote speaker. You can get an acceptable matrix mix using good, high-isolation headphones.
As to stereo:
In the main room it’s a total myth. You may have the system set up as L/R, but that’s just a 2-channel thing. For actual stereo you need 100% coverage of the listening area from both the L and R speakers…or perhaps a L/C/R array. There is only a small area on the center line between the speakers which can be said to hear “stereo” sound. So don’t worry about stereo. In reality it will be indistinguishable from a good mono mix, easier to do and provide the best mix over the largest number of listeners.
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