1) Higher degree of topological complexity. Ridges, caves, rivers, lakes, swamps and mountains. Waterfalls. Zelda waterfalls with caves hidden behind them.
2) More terrain types. Division of current "grassland" into several types of grassland -- heath, plain, meadow. Division of generic "swamp" into marsh, (peat)bog, mire. Division of generic "dirt" into steppe, path, mudflat. Division of water into two-or three degrees of water depth, other possible tiles as well -- river inlet, fresh water, spring water, muddy water. Infinite possibilities for the further divisions of forest.
3) More specialization of each terrain type in terms of creature spawns, plant and resource availability.
4) New herbs, plants and creatures to aid in 3.

Eagles are nesting birds primarily found in mountains: Beaks (mask), feathers (arrows, clothing), claws (bling-bling, alchemy), meat and eggs. Herbs needing high perception to be found. Herbs usable for healing, food, crafting and alchemy.
5) On demand spawning of new maps. No artificial invisible wall, no map edge.
6) Better map handling. In game world map. Minimap updated with map changes.
7) Mine points that can be found much like wellsprings are right now. Mines only buildable on minepoints. Different kinds of metal. Panning for gold, and ability to extract bog iron, would be neat.
We might not do it all in one go, but hopefully we'll do a lot of it. Graphically I'd like a chance to redo the tile transitions, for example, as a lot of them look like crap right now. New trees.
Weather and seasons would be fun, but I doubt that will happen with this reset. It might not even need one. We'll see. A lot depends on where the moods take us.