"Also today, I found myself (again) creating datasets called
"cut1", "cut2", "cut3", etc., as I optimized a parameter (z cut)
iteratively, and wondering whether I could (someday) just keep
recreating "cut+orig" and hit "rescan" and everything would be
fine...."

You could run try this.
(a) compile the plugout_drive program from the AFNI source code
(b) run afni and enable plugouts from the Datamode->Misc menu
(c) run plugout_drive in another terminal window
(d) type the command PURGE_MEMORY into the plugout_drive window
--- this will purge the datasets from memory, forcing a reload from disk
--- perhaps this will work for you, when you replace the contents of the .BRIK file