LG makes a 15" 2.1 lbs laptop. The case is made of magnesium alloy. The specs aren't as good as a MBP but that's not really the point. The point is NOT that I want the LG. The point is that it seems possible to make the MBP much lighter.

Examples: An i7 doesn't weigh pounds more than an i5. 32gig of ram does not weight pounds more than 8gig of ram. 2TB SSD does not weigh pounds more than 512GB SSD. I have no idea if a 15" HD-DPI display weighs a lot more than a 15" 1920 display weighs. The LG even has all standard ports 4 USB-A type plugs, HDMI, etc. There was no need to make it thinner and switch to USB-C mini to get the weight down.

So that basically seems to leave battery, second GPU, case, fans, maybe keyboard and display as what's making the MBP stay heavy. I guess I tend to believe the LG with the same specs as the MBP would be at least 1 pound lighter than the current MPB