His post was actually not about installing in a different directory but rather making the addons folder a symbolic link to a different unprotected directory. The trick is, while NTFS does support links (though they call them junctions and its closer to a hard link than symbolic), there is no way of actually making them from a out of the box windows install. As I understand it there ARE 3rd party programs out there to create junctions, but I have never used one.
I actually doubt you'll get anyone to try this however. I'm sure the developers have already solved this problem one was or another for themselves, and your average user probably doesn't understand what the devil you mean by a symbolic link.