I wonder, if there is so long research, why you have not come to conclusion that the main problem is not reactor/proactor/event loop, but writing actual asynchronous business logic. The industry has gone mostly coroutine approach, requiring special technology support and usually with lack of fine predictable execution and stack control for mission-critical cases. That's the reason why FutoIn AsyncSteps exists as concept and reference implementation in C++, Java and JS/ECMAScript. It is compatible with foreign reactors by design via AsyncTool interface.