The Dell Precision looks like a good option if you don't need a better GPU (Quadro M2000M ~= GTX960m). I've been doing VR dev so I went w/ an Aorus (the smaller X3v6 on preorder), but you may want to look at something like the X5v6 which should tick all your checkboxes save touch and might be more appealing than the Aorus: http://www.aorus.com/Product/Features/X5%20v6

One bummer about this new gen of Aorus' is the mystifying lack of TB3 (despite USB-C 3.1 on an otherwise top-of-the-line-specced system).

Too bad about the P50 having external display issues. A built-in 100% NTSC / 100% AdobeRGB 4K panel sounds great. (same crap Quadro card though)