That may very well be a good approach, though another technology has been roped into the mix.
And there's also the case where I indeed do want my headphones to pair with my iPhone that's 15m away in another room instead of the Macbook in front of me. And not my car that my girlfriend just started on the driveway 10m away. And I want to manage this from my headphones which only has two buttons and some multi-tap gestures.
The trade-offs get complex. Also, your tether idea is still something implemented per device rather than something Bluetooth as a technology can solve with some simple tweak.
In the presence of conflicts, the phone could prompt the user for audio source, then persist it in software until the next time they have a new conflict. It really seems to be an issue when you go from no streaming audio to streaming audio, from the UX perspective, so that should minimize the number of times that prompt appears. Could also solve it by the same way we solve SSID preferences: a static list of paired devices with priority orders and an accessible menu to select a specific one, and then persist that until you change your streaming state again.
Same here. My wife starts her car in our driveway, and my phone connects to it. Which leads to two issues - she has to fiddle with controls to connect to her phone, and then any audio/phone call that I was having at the time is completely lost for me until I can change it back.
And then Bluetooth is just hot garbage in environments with lots of interference - I work at a games studio so we have loads of devkits with controllers lying around, and my pretty expensive Sony Bluetooth headphones stutter like crazy unless my phone is within a foot of them.
And there's also the case where I indeed do want my headphones to pair with my iPhone that's 15m away in another room instead of the Macbook in front of me. And not my car that my girlfriend just started on the driveway 10m away. And I want to manage this from my headphones which only has two buttons and some multi-tap gestures.
The trade-offs get complex. Also, your tether idea is still something implemented per device rather than something Bluetooth as a technology can solve with some simple tweak.