Won't work. The entire STEAM folder must be in the same place. There is a support FAQ on Spectrasonics site that expliciy spells this out for Keyscape users that already have Omnisphere or Trillian. You can move the entire folder, alias it with a shortcut, and install Keyscape to the new location.
By by the way, you must have a Spectrasonics account and be logged in to see the Keyscape install FAQ, which is kind of weird.
Regards,
Dan