I must add that i'd LOVE to see, at least a version (a checkbox to be ticked, or whatever) that also adds environments to the maps upon generation.
It could also use the noise filters that the terrain generation (the physical terrain) uses, to make it appear natural.
Such as, snow near the top and bottom of the map, blending into the standard barren, or / and grasslands near the middle of the map (very broadly and varied), with some nice deserts as are already placed, but mostly on the equator and in more coherent shapes.
And perhaps some fallen terrain in rare places, like a dark valley or peinsula somewhere.
It'd add more variety to the maps, not only the terrain itself, but now also the texture, the same map could have several different looks, an ice world, a normal map with a mordor-lookalike valley surrounded by mountains, or a desert world with occational grassland bordering the oceans or lakes.
Perhaps as simple as making the forest noisemap include grasslands terrain, and making the swamps a bit more random (not just tied to the center of forests).
Maybe the current Barren terrain could be imagined as steppe, or plains (if going by Civ4 mapscript examples), acting as a soft buffer between desert - grasslands, or grasslands - arctic, or anything - fallen. Or even just randomly spread between most to form a natural looking terrain without clear cut borders.
I dunno how much more work it would be, but that remains my wish
The rules in the Perfect World mapscript for Civ4 were very good, although produced a bit too large deserts. Meh, i wish Elemental had a proper random map generator by default, the more i think about Civ4 again