Are you sure about that?

I've looked at the library, it doesn't support anything besides epoll and IOCP, i.e. no BSD or OSX support, no AIO on Linux (the kernel one, not POSIX).

You probably don't want to consume IOCP API on Windows anymore, Vista introduced higher level and easier to use StartThreadpoolIo and friends.

Also on Windows, even with IOCP, you don't want to split async IO from thread pool. The OS kernel manages them both at the same time. Work stealing or other custom scheduling is usually slower than what kernel does.