One of the things that I've often thought would be handy is an in-game notes utility. Sure, I can use Notepad or Textedit (or whatever) to record where shops, pools, altars, etc. are between game sessions, but it would be nice if I could just type Alt N and notes for that specific character would pop up.
Of course, I'm not a programmer, so I don't know if this would be a lot of extra effort or would dramatically reduce the art of JADE and/or ADOM.