My suggestion is this when it comes to currency manipulation. We need the ability to appoint a Central Bank head. So this means a new minister and a new segment on the policy board. Right between Economy and Taxes should sit Central Bank. You have a decent amount of policies already that are strictly imposed by a central bank. No head of state deals with this stuff beyond recommending someone to run the show. However, if we are going to dabble in this, we may as well go full blown.
Hear are some policy ideas that could work. I am borrowing from both Keynesian theory and Austrian Theory. Personally, I’m an Austrian, though I have studied the five major schools of economic thought.
Adjust Interest rates on lending (a slider that goes +/- 100%)
Gold Holdings (the more you have, the more it impacts other policies and their effectiveness)
Gold Backed currency (A slider that goes from Fiat, Fractional reserve, full gold standard)
Debt backed currency (this would make it impossible to eliminate debt, but this is what the USA uses)
(World Reserve Currency)
Also, Hyper Inflation should come with a count down timer. If you run inflation high for too long, you destroy the currency. This should result in a loss in the game, very similar to assassination.
Another option is to simply eliminate the policies relating to central banking and instead simply appoint a Banking method. So Every election year comes with a new opportunity to change your macro central banking strategy.
An example, you pick the Austrian theory. Leading to a gold back currency where debt is expensive but savings ultimately pay for everything. Stability is king but GDP will not flourish so quickly. The central bank is more of a national clearing house that holds the nation’s gold.
Keynesian theory, where a central bank is born. GDP can grow quickly, inflation may jaunt here and there. Currency is either fractional or pure fiat.
Socialist Theory, the Central bank IS the main bank to do business with. Money is Fiat, Socialist policies such as financing for government controlled industry becomes highly profitable. You are given a free loan from the bank every quarter. The debt is held by the central bank and could be discharged. This may destroy stability from businesses.
These are just ideas. However, if we are going to dabble in central banking, I feel their is more room to explore the topic. I highly encourage you to look into the options. If central banking is something you may not want to consider implementing, then maybe you should remove the policies that touch on the topic. It seems very unfinished that way.
Again I love the game!