Current changes to worldgen (like recent addition of differently sized worlds) and the army arc need to be taken into account. For example, more evil could just mean more goblins at some specific date in history and you could just stop time there and start playing. To predetermine history goes against the philosophy of emergent gameplay as the world develops.
A temporary fix for some of these requests, as well as people being unable to find all features (adamantine, flux, sand, magma, etc.), could be an improved worldgen scripting abilities for users. Some examples:
* start generating worlds, when X1% of world is evil, save. Continue until X2 such worlds are generated.
* start generating worlds, when at least such and such resources are within an X1 times X2 square, save.
* start generating world, when there is at least one place where there are dwarves with no potential contacts (notrade), save. This one is really rare.
Then just leave DF running overnight. I recently had to generate about a hundred maps to find a suitable place for some special projects of mine and doing it by hand, then exploring with third-party tools is time-consuming and annoying.
Much later (yay feature creep) this could lead to arbitrarily complex scripting language - generate worlds until you get a mountain-ringed evil land of goblins led by a mythical being, north of it two civilizations of humans in alliance hundreds of years, then a serene elven forest, abandoned dwarven fortress and so up to the frozen north with unded left from a former human civilization.