It seems that the iPhone 6 main selling points could be all about the screen.
First, make it bigger. Say 5”. Second, make it highly resistant. Say with sapphire. Third, make it super high res. say like 2x current retina displays. Give it a name: Super Retina.
Make the device look smaller than current crops of similar 5” devices by minimizing bezels. Take advantage of the spacious inner space and maximize the battery. Forget about one hand operations as people who will be buying this device won’t care too much about this. Sell this puppy with one of these tag line:
"When bigger doesn’t mean too big. Here is the iPhone 6".
“For those who want it bigger. Here is the iPhone 6”.
“For those who want it all. The new iPhone 6”.