In considering how to start a game of Miseries and Misfortunes I thought about the first adventure. While I think you must have a session zero to create PCs for the game the first advenure must be broad enough to allow all levels of French society to participate. From Noble to Child-Thief you have to cast a wide net. I have a few ideas and perhaps you excellent people have a few more to add.
The story begins in a village not too distant from Paris… perhaps its abandoned due the war or plague. The PCs meet up in the deserted village seeking food or shelter (wasn’t the winter of 1648 exceptionally bad?) A threat arrises and requires the PCs who might not otherwise associate together to band together. This threat could be bandits or highwaymen. A cult of some strange diety. Maybe a beast like in the movie Bortherhood of the Wolf?
A fire rips through Paris and the PCs are trapped together in a building, church or even a barge on the river. Now the heroes must try to save others or at least protect themselves from those who my cast them out into the flames. The fire may have been caused by an arsonist whose indentiy becomes known to the PCs. Was the fire politically motivated? Did the fire awaken some sleeping evil hidden in the sewers of Paris and drive it to the surface? In the rubble might a hero find an acient text unburned and full of secrets?