Parsing audio vs reconverting; offering codecs for higher tier licenses

If YouTube video contains audio streams like aac, why not simply purge them from video streams? Just pluck out the audio stream bit for bit, and save it in a container (aac, MP4, OGG...) the system recognizes as the audio stream format?

It's way less CPU intensive, and doesn't introduce any artifacts.

Reconversion of audio should be a secondary option over just 1:1 ripping the audio data out of the downloaded file.

You can also include an audio codec that you license and pay with upgraded tiers on your platform, to include audio formats like WMA (for low bitrate audio books) and OPUS (for low bitrate, CD quality music), compared to the standard MP3 formats, and FLAC for high bitrate, as lossless of an audio as can be (I know, youtube compresses the audio, however FLAC can be useful for people post processing the audio for other projects).

Just a recommendation. Thank you.