There are two known solutions - one is Paser Tec and the other 'jugaad' done by Italia-Linea. But my question is - WHY do you want to retain B&M? It's the most buggy and useless feature ever. And in any case, if you are going for an after market HU, the BT functionality in that is way better than B&M. e.g. in my JVC 926, I can pair 2 phones simultaneously, voice quality is way better than B&M and all other features are the same. If I had an option to buy Linea without B&M, I would have definitely availed it.