"the trade-offs in battery life and camera quality are too significant" - a small but thicker phone would have no trouble with battery life and could for sure have the same good cameras as larger phones – and could possibly even ditch the camera bump if it just made the entire phone as thick as the camera bump to fit a larger battery.

(After all, easiest way to increase battery size is to increase the smallest dimension. Add 1mm to a 4-4.5mm thick battery and you'll increase the battery size by 22-25%. Make the iPhone 13 Mini as thick as its camera bump and you would probably add ≈2.4mm, which would make the battery 60% larger)