> as to be daunting/inconvenient to use

I don't even know how to respond to that. How in the world are you using C++ professionally if you think coroutines are "daunting"? No one uses C++ for it's "convenience" factor. We use it for the power and control it affords.

> What I was thinking of as a state machine with using std::future was a single function state machine, using switch (state) to the state specific dispatch of asynch ops using std::future, wait for completion then select next state.

Uh huh. What about error propagation and all the other very real issues I mentioned that you are just ignoring? Why not just let the compiler do all the work the way it was spec'ed and implemented?