I could see using one to accompany a larger, more vertical system as a controller skiff. Or for more spread-out systems just to reposition a group of modules closer to where they’re wanted.
Or for less frequently used modules just to grab a little bit of space for something else, without expanding to another full case (or just using a bunch if these in the first place to constantly be able to rearrange). Or for small self-contained systems.
I already have my Field Kit FX in a separate box in my pedalboard, where I have to use longer patch cables to work with it. I could see parking one of these beside it with other FX and my pedal interface stuff, perhaps with the ADDAC or Doepfer bridge.