Government banks:
When the Finance DLC is enabled and banks are active, the government can no longer loan out any money
I think this severely limits the game because as we know- governments utilise the central bank to either institute new monetary policy or quantitative easing. Another feature from the game that could be implemented/improved upon.
There should also be a government portfolio, it should be able to invest in companies/buy property (it owns the entirety of the land until players buy it to place their buildings or to buy land and hold as an asset. If the government could also invest, it would make the game more interesting.
Other recommendations:
Variable/Fixed rates for the loans at player owned banks, it doesn't make sense to assign one credit rating per interest rate- and there are only 5 interest rates which means you don't get to set them yourself. They are fixed/quasi variable because they are in line with the interest rates set by the player (in game parameters) and govt (central bank chairman).