Usb c is capable for UP TO 100w. Doesn't any portable device need such a high power? Even the most power demanding 15 inch MacBook has a power adapter of 85w.There's already a lightning to usb2.0 adapter. I use mine frequently to connect an external dac/headphone amp when listening to my shure ear plugs. I also have used it to transfer in jpg from a compact flash adapter. It works but it's super slowe compared to usb 3.0 transfers. Usb-c is designed for 20volt operation. That's how it can carry 100 watts while at only 5 amps. Lightning is currently limited to 5 volts and it would be a risk for apple to up it to 20 volts at the risk of frying iPhones etc with the wrong power adapter. Usb c is already has a standard for this. In fact my wife's rMB usb c charger charges our phones and iPads in a pinch with the right adapter. At 5 volt, you would to dump 20 amps in a very small cable/connector. That would cause a ton of heat.
And I don't see where "frying" iPhones coming from. Don't you know that those adapters adjust power transmission automatically? Did you forget the chip inside the lightning cable/connector? That's where advantage is. Soon there will be lightning-usbc cables on the market, I don't think plunging such a cable into a 28w apple usbc charger will fry my iPhone. And 28w should be plenty enough for such an arm based ipad