How could that work in EU4, Leviathan?
- Do away with the whole loan system. It's a leftover from EU2 (EU1?) and was never any fun at all. Let there be some other way of managing your finances.
- Let there be some sort of recruitment system that is tied to the ruler's abilities / properties. More ups and downs, when he dies.
- Don't have the economic system be so boringly predictable. Make tax yields more random. Good harvests, bad harvests...
- Do away with "minting"!!! It makes no sense at all. Look at the ideas that the Magna Mundi people had.
- Do away with player-controlled, 100% predictable tech progress.
- Have more things that a player can introduce, that boost him for some time, but that he cannot count on to stay forever. Example: Manufactories. Make it so that they aren't so insanely expensive, but also don't stay forever. Like when you invest money to start a porcelain business in your provinces, make it so that it stays for at least, say, fifteen years, but can fail after some time. Economic management should not consist of saving, saving, saving, saving, then building, then twiddling thumbs, then again saving, saving, saving.
Also, have there be sliders that influence how often you get what I would call opportunities: "economic ventures" (= opportunities for land amelioration, for novel businesses, merchant expeditions etc), "military ventures" (= opportunities for fortress constructions, reforms, military tech innovation, raids into neighbouring provinces, etc), "ventures in state affairs" (= opportunities for splendid festivals, marriage alliances, diplomatic expeditions like Zheng He's overseas expedition, and so on) Opportunities are a mix of stuff that has likelihoods to appear (random events, essentially) but that you can "provoke" into appearing by giving continuous funding into the general "ventures" category. To make things less of a random experience, have there be progress sliders where you can see how likely certain opportunities are to pop up. Like the tech research progress in Master of Orion II, where you would be given an "expected" date but things could come to fruition earlier, or later. Some things are, after all, fairly easily planned (like starting a land amelioration initiative, or throwing a festival) but others depend on opportunities to present themselves... a foreign monarch coming to the realization that you are a prestigeous state, and offering his daughter's hand, for example. Or finding an enterprising navigator to start a journey of exploration into the Pacific.
Essentially, leave behind all the EU2 baggage. Put the axe to all of the old EU2 features that were carried over into EU3: minting, predictable tech progress, loans, navies that you command around like land units and that never suffer storms or unfavorable winds, and the endless save-save-save-save-spend-repeat grind that you go through for EVERYTHING in EU3 from manufactories to modernization and so on.
All of these save-save-save-save-spend-repeat schemes make EU3 a long term planning game, where if your plans are derailed, you are completely set back or may have to switch goals. It's really a grind in so many aspects currently. But running a country should not be an endless waiting game where you watch your gold or your stability slider or your tech slider inch forward pixel by pixel. It should involve unpredictability, opportunities, ways to bypass the waiting lane. Ways to have dazzling and unexpected breakthroughs, and also have terrible setbacks, but setbacks that you can RECOVER from.
CK2 does that very well. You may lose your best titles, all your money, all your prestige, but because each ruler is a new opportunity, none of that needs to dishearten you. Sure it may frustrate you, but it's not game over, after rain will come sunshine. Something that is TOTALLY lacking in the EU3 experience.