If you use Masterwork, you can become a vampire or a necromancer by using in-game resources. Basically you CREATE all the towers and evil types you desire. Possibly make bogeymen turn whatever they kill into a zombie, or even have an evil rain create zombies as well as husks or thralls. Mod wildlife to throw up a 1:10,000 chance caste that is a mega-beast, (several sets of castes + several populations of animals = many different variations on megabeasts that can be met by adventurers and forts alike.) With the right modifications of existing systems, we can make the basically static after-world game seem more dynamic.
Meta-rules like "a new embark in a civ must have at least one edge adjacent to a pre-existing embark or the starting town/village in that civ" would simulate the growth of the various civs in world-gen and the building of roads would just be another set of long, thin embarks.
Modding all races to produce cities, roads and the like (like humans) would make them create markets, keeps, dungeons and such, even from year 1. I've seen it enough in Legends mode being all built in "1".
All wars and the battles within them would be fought between the various playable civs with the other (static) races taking the brunt of the action, but using DFHack's "tweak makeown" in adventurer mode (or with "embark everywhere", in fortress mode), you could "draft" those of different races into your civ - basically you'd be conquering their villages and towns. Suddenly multi-racial civs become a viable option (especially if you mod dwarves castes to throw in "half-dwarves" that get some of the stats/descriptions of the other races too). Yay for ethnic diversity and half-kobold adventurers really good at sneaking!