HUD should be no problem. I don't have it on my E70 but my E60 M5 has HUD and it works fine with an Avin head unit. Most (all?) of the Android head units let you access the CCC/CIC system.

The factory backup camera is likely a nuisance. It will work when the head unit is displaying CCC/CIC, but that won't happen automatically when going into reverse. I removed the factory backup camera on my E70 and installed an aftermarket one that connects to the Android head unit since I use it with CarPlay 100% of the time.