FYI, you don't have to limit yourself to the hard edge of an output for a mix. I have done plenty of LED systems where I've used a TH2G to drive multiple scalers so that I can have as many mixes as I want.

Hypothetically, you could scale to the left side of an output and make that a mix and the right side of the same output and make that a mix also. There are canned settings for the mixes but you can also adjust them in any manner you want.