I think that mono/stereo setup of inputs is saved or altered at the Show level, Not at the scene level. (I recall that this is dictated by hardware and not likely to be altered in future firmware updates).
In your situation, you need to save a different Show for each band, even if each band only uses one scene.
In Version 1.4 Ganging was introduced. So you can link parameters of two, or more, Channels. This will help to realize Stereo channels. Or you can define some stereo channels on the end of the inputs and then use them in different scenes with differen input patches. And because the layer strip assignments are also stored to scenes you can rearrange the strips on your working folder as well. The same you can do for mixes too.
Thank you so much for the answers!
Ganging channels is really good for input linking. But for the stereo mixes works only change the show. And how safe channels will work with new show?