I’ve tried similar with Apt-X BT dongle (Sennheiser BTD-500), and I had almost success. My initial aim was to have a BT speaker (Philips fidelio P9) connected to my RPi (running Max2Play on it) vie the USB BT dongle. It worked well, with some bottleneck: first time BTD-500 and Philips connected/paired well, but when I switched off the speaker (ie for night), and turned on it again, it does not connected to the BTD-500, while I removed and re-plugged the dongle again. Even if Sennheiser says, it remembers the last 3 or 4 connected devices, it does not connect anymore only if I replug the dongle. The dongle shows as connected (lighting blue led), but Philips still looking for active BT connection. It is very unconvenient if I have to remove the dongle every time, when I want to use my speaker. So I gave up, but definitely you can add a BT dongle to Max2Play.