Yeah, I'm sure deep down you sensed it wasn't host supported
I think maybe it's a chicken and egg thing: no host support it, so no plugs use it so no hosts need to support it. Some hosts that support MIDI out from VSTs (like Ableton Live) don't support it from AUs, maybe because they have no plugs to test it with?
I'm not really an expert, but I thought if you used the OSX midi stuff you would not be able to get accurate timing?
I could post my code up, but I'm a bit hesitant as it has never been run! It does compile though. If you really want it though...