It depends on how useful the command line program would be. Some things, like plotting a route on a map, or playing a 3-d game, just don't lend themselves to a command-line interface. But other things, like system tools are much better from the command line than from a GUI, for the simple reason that they can be scripted.

Dr. Richard Hipp once said that his ideal GUI operating system was a blank desktop with an icon to open up command windows and another icon to open a web browser. I feel almost the same way. If it would be useful as a command-line program, and not too difficult to build that way, I would do it. The GUI could be a completely separate program, maybe built by someone else!