I agree with most of the remarks, having the same experience of finding expert too easy (Biz, starting in high)

Starting in late is definitively an option, but Galestrum is right on missing 2/3 of game : it is highly satisfaying to take a faction very early and take it to the top by seeing successive upgrade. One solution is to refrain yourself from conquering any non rebel province for the first 100 years.

Good idea on the spy cap, Dr No