This is indeed an interesting and thoughtful write up...
I agree with your views. If exponential growth/action is properly managed the possible downsides won't be a problem to think about.
However, just like you mentioned here that

In a real economy however you have to worry about many things, money supply, debt, interest rates, tax burdens, tariffs, energy costs, commodity costs and so on.

Controlling inflation and debts accumulation for example, as demerits of exponential is not at all an easy task. Governments may make just one mistake and to rectify it becomes a heck of trouble. Take for example, the Zimbabwe case of hyperinflation which I believed arose from the decision to reshape ethnic balance in land ownership. That was a good idea they thought, only for them to find out otherwise. The country at a point had to switch almost completely to the use of US dollars as her day to day trading currency.
My first read this morning, and I must say I enjoyed it.. Thanks @procrastilearner