Inspiration can strike from odd places. One particular source of ideas for creating this Early Modern Campaign setting and general feeling is the 1992 Microprose game Darklands, a contemporary in the great era of games like X-Com and Civilization.
Darklands is a sandbox RPG set in the Holy Roman Empire in the 15th century. The setting concept is unique and very enjoyable. Essentially, you are playing in 15th century Germany as imagined by the people of the time. In effect, superstitions, rumors, myths, and legends are all real. So pagans really do meet in Covens to sacrifice the un-Baptized to summon demons, Gnomes live in deep mines, and Dragons roam the countryside along with all the other things that go bump in the night. More interesting, 'magic' is performed through the intercession of Saints and alchemists can create wondrous potions with a philosopher's stone.
The mundane is covered as well, from encounters with pilgrims and traveling clergy to corrupt Raubritters (robber barons of Medieval Germany) and a well presented, historical social structure. Travel on foot by road or overland is long and perilous, whereas the best way to make a long trip is on river transportation. Cities are named historically and linked by the actual rivers in Germany, making for a good representation of actual geography. Other touches go a long way to making a fun, believable setting, such as how camping in the woods on an estate owned by a local noble runs the risk of a confrontation or the fact that not every village is friendly (and might house witches preparing for a coven!).
The game is also emblematic of sandbox play. There is no hackneyed plot development right in the introduction, no call to arms or quest to complete soon as you press Play. You can go a good while playing around before you even find the first thread of the overall plot. Plus, the game doesn't end after the final confrontation, allowing further play.
It's amazing that the game captures so many aspects that I want to have in this EMP game. A marriage of the realistic with fantasy, a strong nod to actual history (all the Saints are the real, Catholic ones), and open ended game play. A strong tone is set that parallels low level play in D&D, namely, at the beginning of the game, you are very mortal. However, there is nothing stopping players from tackling any challenge and even having a chance at success right at the game's start. For example, dealing with a Raubritter by challenging him and his retinue of men in their own keep is suicide until your characters gain in strength. However, you can still attempt and succeed at assassination and sabotage, either sneaking in to fight the Raubritter in his bedchamber or setting fire to his keep. Darklands is a great representation of many of the tenants of D&D in video game form.
The game itself can be found at your local abandonware site, like Abandonia.com. I don't think Microprose will mind anymore.