Yes - Michael. If your goal was to maintain compatibility with the latest and greatest AOLServer implementation, then you'll have to maintain a Win32 port no matter how it connects to IIS.
If the goal is just to have a Windows-only version of OpenACS,
then the shortest path would be maintaining an existing 3.x version of AOLServer that supported Windows, and backporting whatever AOLServer functionality OpenACS requires.
If an IIS front-end was a requirement, then maintaining the aolserver isapi filter with this version of AOLServer is also probably the easiest way to go (though not necessarily easy.)
