Custom White Balance

[drufi]

Is it possible to add custom white balance settings (not just presets, but real one like set from gray card)?
I know that with dng I don't need that but for quick jpg output it will be awesome :)

[lahdekorpi]

This would also be awesome for photos.
Having the ability to lock the white balance so that when taking a lot of photos, I could just fix the white balance in post once and copy it to all of the photos...