Certainly the concept of inflation and bank interest is very real and it increases the fun but,
Inflation is rise in general price level, but in this game only the original cost of the business rises while the income stays where it is. I think the income too should rise.
Secondly, Inflation rate remains constant, though in real it is near to impossible. I think if you add bank load concept. That one can take limited loan [limit set by levels] in return he pays interest to the bank. And a deadline by which he/she has to return all the money, or the bank could confiscate the pledged business of the same amount.
Thirdly, if inflation rate and bank rate keep changing, I mean suppose they do so in the game, it will make it more exciting, since it will be up to players to decide when to invest or when to save.
Since the value of the money won't be the tomorrow, it will also add a sense of surprise.
This way players can try to predict and invest in business when they are cheap, and then inflation makes them huge profits, or they have saved money in bank, while the interest rate is lower than the inflation rate. That means originally they are losing money.
Certainly interesting but possible too complicated to implement. Would be an awesome addition tho.
More than the complication to implement, it may be too confusing for the rest of the players to understand how the number are working... ideally we want to keep things simple & fun. Thanks