One of the things I was thinking about with regards to pause and or save games, is the need to control all aspects of real time logic, with possibly stopping/resuming, and saving it to disk is how our current ways of doing async is incredibly lacking.

Unity has introduced the idea of coroutines (which were essentially yield based generators), and people started using them, and immediately encountered problems with pausing/saves.

Internally these coroutines compile down to state machines with opaque internals which are not necessarily consistent across compilers/code changes, and its very difficult to accomodate needs like pausing when using them.

From what I've seen, the usual answer is that people go back to hand-written state machines, and go through the pain of essentially goto programming to fix these issues.