I know what you mean... imagine trying to hide stuff under a 30”x30” table like mine. Even worse with my Large System, which has NO space underneath. If the backup gear is not built into the rack, it usually sits out in the minivan. When I use my Large System, my Small System goes too, but it stays in the minivan, because there’s generally not a good place to hide it from view. It’s in a big black canvas roller case, so it’s not ugly exactly, but it’s a big black thing that takes up space and looks out of place. I’ve worked venues where they provided a small storage room, but I still don’t take backup gear inside that’s not built into the rack (mostly to minimize trips back and forth to the minivan). That can be risky if there’s a pretty critical failure, because running out to the minivan, bringing it inside, and getting it setup can take quite a bit of time... depends on how close you can park, which sometimes isn’t very close.... I am certainly not gonna bring ALL of my backup gear into the hall. There is no room under my table to hide it all!
Having two computers built in (like I have in my Large System is good. It takes really no additional time to turn them on and have them running simultaneously. Problem is, There’s no backup for the Denon MC6000MK2 controller or the Denon DN-410X mixer. I can bypass the mixer if need be, but a controller failure would be pretty catastrophic.
Having a second controller/tablet setup like I have with my Small System (DDJ-WeGO3/Surface Pro) actually makes my Small System less of a risk. Now, have I ever had a controller failure???... Nope (knock on wood(en head), but it COULD happen. I worry about it. I could still play music from playlists on the backup computer (which is my current contingency plan for a controller failure), but actually mixing (without my controller) would be difficult.