I wish the AirPod case had a headphone jack

I have a genius idea that I’m sure Apple considered and then rejected: build a headphone jack into the carrying case. When it’s plugged in, the case becomes a Bluetooth audio transmitter for anything, including (especially) airplane infotainment terminals. Heck, set it up with a double tap of the pairing button to put it into receiving mode so you can use it as a Bluetooth bridge to get audio to your old car stereo.
I can easily guess why Apple didn’t make this very simple twea