AIO support has been added to our 4.1b1 release, you can give it preview, just change the version number in the download link to get it. This build only use AIO, tried it on a server with high disk I/O.
High I/O wait should not be an issue with it. We already got some positive feedbacks for it.
Our solution is based on POSIX AIO, so it could be available for platforms other than Linux as well. It still can take advantage of buffered I/O, as O_DIRECT (direct I/O) is not required.