I think the thread should mention not BENEFITS but ACTIVITIES.
Ya know, what does it change if during peace you got X gold or whatever? Nothing. You sit bored at peace and now you wait not only at manpower regenerate and truce cancel but also bonus to amass. Currently peacetime already has obvious benefits - no WE, fully enabled diplomacy and trade, not necessary full unit maintenance, manpower regenerates - but adding more static modifiers or even worse: penalties to war isn't going to bring more fun.
Instead I support any sophisticated peacetime system such as this brilliant one mentioned above. Something cool, active, developed and constant. In the end war will be always more interesting but peace can be cool to as seen in many strategy games.
Suggestions:
- Developed faction system for all nations (different for monarchies, republics, pagans, buddhists etc)
- Adding Intellectual Life, Science, Art and such other ways for achieving national glory: bring back and reinvent Cultural Tradition, allow on arts patronage, fund research, create academies of science, solve religion vs science dilemmas, or
- National Identity Meter. Devs mentioned that the main theme of eu4 is colonization and establishment of national states - the second thing is absent. Reinvent cultural acceptancr and such stuff in National Identity.
Essentially National Identity represents how people of your state identify themselves with country, are they willing to live in it and die for it, the ultimate goals for eu4 empire is not only establish geopolitical power but construct a nation. There are many ways to improve National Identity or ruin it. Opressive Muslim despotic sultanate governing Hindu masses and conquering random stuff has horrible NI. However there are many ways to build common identity:
- Religion. Establishing certain rites and powerful spiritual bond can forge a nation - historical examples: Sikhism, Judaism, Islam->Arabs, Hinduism, Orthodox Church-> Mother Russia, Church of Ethiopia, Shinto, Buddhism in Myanmar and Tibet. Unite your people under banner of Truth. And spread it to faraway lands along with your philosophy of life, thou shall bring harmony and meaning to the world.
- Ethnicity. Influence and shape cultural bonds to emerge as united nation and unite your perceived 'ethnic lands' and finally become (relatively) united nation state while trying to assimilate other cultures; examples: France, Japan, China, Spain, England. Spread your lingua franca until people will adopt it. Defend Motherland. Historically Poland was going this route via Commonwealth quite succesfully in 16th century but screwed it up at 17th, still Belarus and Lithuania were heavily polonized for centuries. Make people care about the glory of a nation' make nation their source of imperial proud.
- Prosperity. Unite people of many cultures and religions basing on rational human interest, on will to live freely and decently - forge common interest and tolerant way to include Other into it and emerge as melting pot. Examples: United States, generally various colonial nations, maybe Netherlands, modern Singapore. If we are trying to put all countries in these categories, Hordes and many confdderations could fit here because for example khanates were united basing on the prospect of loot and glory.
This is a great triumvirate. You can don't care about it and emerge empirr with steel, blood and personal wishes of god-king but sooner or later you will face an inevitable fall of society where people don't care what banner are they living for. This happened to many ephemeric states born from bloody conquest and fallen via bloody internal conflicts. You can create your private property, mr Tyrant, but prepare for war with your own society... War which will eventually lead to the fall.
So, there are three ways to achieve National Identity. National Identity serves both as meta-goal of the game - as a target and source of reworked Score system - and as base mechanic of the game, as society with bad NI is a revolt waiting to explode and civil war ready to attack after death of every monarch. There are three separate meters: Faith, Nation and Prosperity, and you slowly gain higher levels of them enabling stuff from somethint resembling 'tech tree'. System is fluent but usually you have to choose from conflicting options - assimilating 'lesser cultures' is radically different from buying them with prospect of better life or uniting under banner of religion. You constantly make choices when you manage cultures from new Culture interface - cores, converting culture and religion, humanism and tolerance, diplomacy and economy, evrything affects National Identity. Pursuing NI gives you awesome stuff and unlocks special 'powers' available only from particular paths, such as unique governments and decisions.
National Identity system is connected to factions: Nobility, Priesthood, Medium Class and Peasantry. Each of them desires other things and you have to balance among them while using them to spawn National Identity. Nobility prefers Ethnic Glory, medium class Prosperity, priesthood Faith, peasants are the most flexible. It is possible for all of them to have high willingness to cooperate with You but it is not easy to achieve and maintain.