Marc has nailed it here for me. On the rare occasions I use the 'exploded view' I want to be able to tab between the windows.
I mainly use Alt-Tab and Alt-backtick to move between applications and windows at present, but adding a keyboard mode for switching within the dash would help with organising workspaces by task irrespective of application...
The 'exploded' window view shows windows on current workspace so being able to select one from the keyboard means I can group the windows by task/project in different workspaces.
EDIT: I seem to be have been a bit confused before.
I think some functionality along these lines should be provided by the basic GS though.