Apple opened up its MagSafe tech to the new Qi2 Magnetic Power Profile standard, which "will also support new types of accessories that magnetically attach to the back of the phone, like an extra battery."

Presumably that support would include the signaling for the charger to tell the device that it is an external battery. So there's a path forward.

https://www.wirelesspowerconsortium.com/qi/#qi2