With the digital mixer, the limitation is based on imagination!
Creating Groups for a selection of channels for a particular scene or condition, is a great facility and I usually use this to group the scene channels before and the channels for the next scene; depending on situation. That way I can set the scene, have it running and then move on to the next scene, mid current scene, etc
However, having the channels in sequential order as they are hard-wired is rather limiting. Because you might want channel 1 of the duo and for other scene stuff, channels 4,5,6,7 and then channel 15 for the other part of the duo, and so the duo channel are not next to each other. Therefore, it is difficult to control them. It would be great if you could order the channels in the Group for ease of quick control. OK so this might cause a little confusing if you have to do a hard-wire fix mid-scene, but these are rare and you can go back to the Main for logical hard-wire sequence. Given that I have already selected channels from a 64 channel mixer and aptly named them, the hard-wire reference really becomes unimportant, and so why not be able to move them around. When each channel is selected I can see the actual physical channel on the scroll bar anyway or go to the Channel settings. However, even at that point I don't care what actual channel it is, as I have done all the wiring stuff and now I just interested what is on the channel and the easy of control. This is more for theatre than anything, but it would be useful for bands too.