Nice video anbodearg, that Bose Soundlink Mini sounds good where did you have it placed in video there?
I had no luck with on-board BT just tried dongle with my soundbar and its working good. 
I notice that the audio is out of sync by second or so maybe its because im using v17 krypton test builds. Looks promising so far.
I read that the raspberry pi have put an update to the onboard BT so maybe this will help with this when sam updates it.
Im using the official 2.5a power supply and have had no issues with the rainbow icon.
@sam_nazarko I’m testing this feature on a seperate system as i want to keep my main system as stable as possible so is there a safe way to unistall this bluetooth a2dp testing if i decide to try it on my main system or should i stick with the testing system. I suppose i could just make a clone of my system onto another micro sd incase anything goes wrong. Thanks for your work OSMC is getting better everyday