The problem with having a cap on the level of central bank is that your economy flatline when you reached a certain size. As Qing China I was able to reach central banks level 250 around 1870s which means that I cant grow the economy past around 800-900 million pounds as the demand of money far exceed the supply which mean that the industries are getting less profitable and sometimes lead to shortage of money. I tried to fix this problem by changing the monetary policy so that I can print more money but the inflation keep rising which makes no sense as even though I change the policy to devaluation 25% which increase the money printing, the demand of money still far exceed the supply by at least 25% with this condition deflation should happen NOT inflation. Another problem when there is a cap in central bank level is that it is almost impossible to build more industries which links to the stock market problem. As economy grows and stock market grows the demand of company stock increase drastically but I cannot build more industries to satisfy the demand as the industries also become less profitable due to shortage in money and decrease in the output due to shortage. Which means that the stock market can have shortage in stocks which reduce the productivity of stock market. Moreover the standard of living of the population also decrease as the money demand exceed supply as the populations cannot satisfy their need of money. My average standard of living always stay around 10-11 even though I changes the taxation law to proportional taxation and put the tax level on minimum and also don't levy any tax on goods and services which is really frustrating. The other problem with not being able to expand my industry due to money supply shortage is that my unemployment during mid to late game become really high and I have to enact the social welfare law just to keep them from starving to death which also put a strained on my finances as the social welfare cost is through the roof. Just to keep my unemployment down I enacted professional army and maxed the barrack level on EVERY states in my country and change the infantry type to irregular infantry and mothball all my division so that I decrease the level of radicals in my country due to unemployment somewhat. Lastly the demand of mining stocks does not increase proportional to the company stock which makes the supply of mining stock exceed the demand of it and decrease the productivity of mines.
( sorry for my poor english I am not native speaker) ( also how to produce railway stock)

Fyi I love your mod it really add flavour to this game but these problems really frustrated me.