Bluetooth sounds fine, but it can introduce latency that you wouldn’t experience with a direct connection. Which is fine for listening to music and even video calls are ok, but a minor proportion of the population working on music production will experience that latency. On a smartphone that’s a pretty rare use case, so it’s fine.

Batteries: I extended the life of my 2010 MacBook by swapping the battery and it was very easy. Apple is going to come out with kits for amateurs to do part changes themselves for the iPhone, where that part change will be harder (broken screen swap) than swapping out a MB battery.