And... we have a response from BMW.
Per BMW, post-03/09 build E90's DO NOT NEED TO BE CODED.
So they want to 'uncode' my Alpine upgrade, removing the 676 from my VO. This will restore the volume of my BT/gongs/nav to their original value. It will also restore the EQ of the head unit. So it will then sound like crap again, but this time with supidly loud gongs (even when turned down all the way) Fannnnn-tastic.
I'm not bringing it back in to get this done. I'd rather find out a way to work out some combo of settings with NCS Expert on my own, or live with it the way it is.
Thanks BMW-- thank you for leaving me (and others) hanging on this one. I'll remember this when it's time to buy a new car.