Re: WWJD (What would Jobs Do)
I don't think Jobs would have used a case. He and Jony put a lot of effort in the the physical appearance of the iPhone... and getting a damaged phone replaced wouldn't exactly be an issue.
As for the wider comments on how Jobs would feel about screen size and such: Didn't Steve leave behind like 5 years of plans for the future of Apple? I thought Jony Ive mentioned that the iPad Air was part of that extended plan... I would also assume that he was actively involved in some aspects of the ideas and designs for the iPhone 5, considering it was likely in development before his passing. There is also documented email conversations where Jobs addresses the idea of a lower cost iPhone. Whether or not this directly led to the iPhone 5C, I do not know.
I'm not sure if his future road map was detail oriented on specific features and design decisions, or more of a generalized direction for products and strategy, but I don't feel like Steve would be against much that Apple is doing today. I think the iPhone 6 Plus is the only device really pushing the boundaries of what Steve may or may not have approved of.