So ONLY the camera, battery, bezel, and footprint are keeping it from being the ideal phone. That's an awful lot of ONLYs.
IMO, the Xperia Z2 is a lot closer to being the ideal smartphone--just needs to trim a lot of bezel to reduce overall footprint. It has a terrific camera, big battery, solid build, a fairly light software skin over KitKat and is waterproof, all while matching or exceeding the new One in RAM, CPU, display size, expandable storage, and stereo speakers.
Well, part is design. I prefer the design of the one more and I prefer sense to timescape (I think that's what Sony skin is called).
But yes, if Sony could significantly reduce the bezel and footprint it would be the best phone out right now. It may be the best phone out now regardless.