Getting the info into the tag. Do commonly used rippers/taggers add this info?

The normalize package will calculate them afterward and add them to tracks. I have no idea if an equivalent exists for Windows.

Of course, this isn't "really" what we want either. Really, we want an ioctl to tweak voladj, and to do true dynamic range compression (or expansion as needed) based on the true intent of the RVA2 tag.