I remember that thread, and I really wish I could find it again. Was a great write up, and basically was IMHO the best way to "trail proof" your air suspension system. Only thing that could take you down at that point was a blown bag.
It's really not needed if you have a GAP iiD tool already. The switches wouldn't do anything the iiD doesn't already do plus much more, like the ability to manually inflate each corner separately. There's nothing wrong with having both, or installing the switches if you don't have an iiD tool to provide a work-around, but as noted switches (or pulling fuses) is really a half-measure. That only prevents the truck from dropping. If you've experienced a fault you still have to have a way to clear it and get the truck back up to the height you want, then you pull the fuses or flip the switches to prevent it from lowering. You'll need something like the iiD to do those first two things, so why not just go ahead while you're using it and set it to 'Build Mode' - thus disabling the suspension the same as flipping the switches or pulling fuses. They'll both get the same result, it just seems like work you don't need to do.
There may be one situation I can think of where the switches could come in handy, but it's a long shot. This supposes you've run the switches to the dash or somewhere you can get to them easily while driving. If you're driving and get a red suspension warning light that starts to drop the truck to the bumpstops you could quickly flip the switches before it lowers all the way. Then, if somehow that red warning was coupled with a failed compressor such that you couldn't re-inflate using the GAP tool fast action on the switches would have kept you inflated when the iiD would not. But that requires a very particular set of circumstances and quick reaction on your part.