Probably pretty impossible, but I have dreamed of a dynamic, general-purpose GUI that adapts its display for the selected utility. On selecting a utility, the GUI app would parse the associated man page and create GUI widgets for the various options available. Well, maybe not the man page, but you get the idea. It's not a hard-coded GUI but a dynamic one capable of supporting multiple utilities.
It could also offer simple interactions between supported utilities such as piping.
High on my list come graphical file tinkering utilities such as ps2pdf.
So for example I could take a pile of mixed graphics & photo formats, convert them all to pdf and merge into a single, paginated print file, all with one tool.
Also high on my list, but probably not on many others, comes Adrian Rossiter's Antiprism
toolchain for displaying polyhedra.
The ultimate dream is an OS where, by design, the CLI and auto-GUI both hook into the same user service function and so by definition implement the same functionality and are genuine alternatives. Other UI's - audio, tactile, etc. could also hook into the same user service.
"Klinger, do you know how many zoots were killed to make that one suit?" — BJ Hunnicutt, 4077 M*A*S*H