Completely disagree. Dongle dacs are noisy, easy to break, etc. The dacs in phones were fine, easily transparent against whatever else is external and bulky. If you’re worried about the cable, use headphones with replaceable cables.

Having a jack also doesn’t prevent any of the other options. No reason not to include it.

Yeah that wouldn’t really do it. That ignores the boneand body Conduction which would be a significant contribution to the sound you hear. I’d expect a huge low frequency boost.