While it was fun to do the papercraft (so yeah, i actually printed it out =) ),
the form factor makes no sense at all.
The widescreen aspect ratio for the screen in the iPhone 5 was a really bad choice by Apple (as can be seen by contender devices being both taller AND wider in screen selling great) and the only halfway proper argument for only gain in height and no gain in width was in being able to say: "but, but.. you can still use it with one thumb!!"
So, now, when making the overall size larger, so that one can't use it anymore with one thumb/hand in some situations, it would make ZERO sense to stick with the stupid widescreen aspect ratio. It would then make way more sense to go with the aspect ratio of the previous iPhones for the screen, so that one then gets a proper gain in width, too, not mostly in height.
Besides that, i'm all for a larger screen, cause yeah, most people should be able to use a phone with two hands in between (which one does for many apps like many games anyway) and besides that even when using it with one hand one doesn't have to constantly reach the opposite furthest away edge with the thumb all the time.
Also the larger screen smartphones only feel weird when first seeing them, after using them for a while they feel great and the iPhone screen feels tiny.
The only big downside would be if it comes with lowering the ppi and especially bummer: If Apple still doesn't properly upgrade iOS after all those years, it has to be updated to make proper use of the more in available screen real estate and besides that, yeah, iOS just overall feels super boring by now. Good still, yes, but yeah, not really fresh by any means.