A couple watts of heat dissipating into your face and head the entire flight is.... Not optimal. Heat is a rather important issue for VR hardware. You can't really positively ventilate the actual part that goes over your face, or else you dry out your eyes and that's pretty unenjoyable.
The battery is not located near your face, it’s lower on your waste. I’ve never experienced heat up on my quest 2, and I’m using it for mostly sweaty things. I just can’t see Apple making something that gets hotter than a quest.
This is news to me, I've always had low amp USB-A slow chargers in economy. Those old cigarette outlets can deliver 75 watt, but no idea about the amperage.
I am sure USB-C with PD will be available at some point, but it's not a majority of economy today AFAIK