Yeah, there is no automatic way to do this - you’ll have to rebuild the plugin source so that you can call the lower level Bink API. In that API, you can call BinkOpenTrack, and BinkGetTrackData each frame to extract the raw Bink audio data, and then pass it down to Wwise.
You can also snag in at the post mix stage, and then we send you down 5.1 audio channels after all the internal mixing and volume scaling has been performed…