Scratch disk location customization

What I'm after is to be able to choose more than the root of a drive. I.E. a specific folder on a drive not just the drive itself. 

It would be interesting to hear from one of the Photoshop software engineers as to how that would or would not affect anything.  Before we had SSD storage, I used to take the time to set up a volume/drive just for the Photoshop Scratch Disk and use it only for that; however, I think it's been 10 years or longer since doing that.