a more realistic overmap mode with variable visibility and without automapping
EDIT: reorganizing this post. A few suggestions for a more challenging/realistic wilderness orientation experience.
From the 0.0.7 video, apart from the overmap size, the other difference with ADOM seems the highlighting options to distinguish between the area that is currently visible and the area that isn't, but that you've seen earlier. Cool!
How about the following, implemented as options:
1) Only the currently visible area is shown. No automapping of the areas you've passed through. You never (at least not by normal means) see the whole world. Coz real fantasy heroes don't have time for continuous mapmaking! They just get lost a lot and thereby stumble upon new adventures :D
2) Different terrain and weather give different visibility ranges. If there were some altitude map this could also make a difference (e.g. no visibility range at all in dense woodland except at the top of a hill).
3) The overland map changes orientation when the player changes direction; i.e. the player moves on-screen in only one direction but the map turns around him/her. Combined with suggestion 2, could really throw you off-track in dense mist etc. (But I don't immediately see how this could work for diagonal movement.)
4) Telescope and map items - the first increase your visibility range; the second show part of the world you're not currently in yourself.