Here's a new name to conjure with,
Philippe Buonarroti who seems to have been a promoter of conspiracy as a means to pull down entrenched monarchies. Where
Adam Weishaupt (also trained as a lawyer) seems to have done little but get himself in trouble, Buonarroti seems to have been regarded as a fountain of practical advice and a toiler in the vineyards of revolution.
This man, who wrote at least seven books on the practical details of running a revolutionary conspiracy, seems like a great source for alternate worlds. I ran onto the name while reading
Eric Hobsbawm's classic book
Primitive Rebels. Although I don't see this book as a great source of alternate worlds, but it can be strip-mined for interesting opponents and movements. Hobsbawm, because of where he looks in history is a gold mine of alternate paths for the 19th and early 20th centuries.