Hi Tim, Hi Mark,
just recently I had a similar issue when I was integrating a Raspi B+ into an old tape recorder from the good old 70s (see photo attached) to get some web radio features using the music server mpd/mopidy. For user input I connected the buttons of the music tape system via GPIO and got the PiScreen for doing all the rest (selecting radio streams and composing play-lists).
On the hunt for suitable software for this purpose I looked into xbmc/kodi to serve as a play-list editor. However that seemed a little over the top. Then I stumbled upon the mopidy touch-screen extension (mopidy_touchscreen) hosted on github. This extension (as seen on the photo) is written with pygame and there is no X server in need.
Possibly the pygame library might serve as a framework for simple development of basic user input GUIs for the PiScreen.