The UK has the 'Doctrine of Lapse' events, with the following trigger:
Code:trigger = { ENG = { NOT = { has_country_flag = empress_of_india } } vassal_of = ENG ai = yes civilized = no NOT = { prestige = 15 } OR = { primary_culture = assamese primary_culture = bengali primary_culture = bihari primary_culture = manipuri primary_culture = nepali primary_culture = oriya primary_culture = sinhala primary_culture = avadhi primary_culture = kanauji primary_culture = panjabi primary_culture = kashmiri primary_culture = gujarati primary_culture = marathi primary_culture = sindi primary_culture = rajput primary_culture = kannada primary_culture = malayalam primary_culture = tamil primary_culture = telegu } }
For people who don't know much about modding, this means that every now and then you get an event asking if you want to annex one of the indian states. So after a while, you have annexed most if not all of India.
Prussia (or technically any other German state) can form the NGF and then the German Empire if the sphere certain countries, and, in the case of the Empire, have Alsace-Lorraine conquered from France. These are both decisions, by the way, although German unification can also be achieved by events, but I believe that is far less likely.