Just to add the same that everyone said, with my humble example:
I have a 2010 Macbook Pro that still works today. The screen is great even today, the keyboard, trackpad and audio are very good, the case is well preserved, everything is good in it (except the battery, but that is changeable). But it is eternally a dual-core Sandy-Bridge processor, with 8GB RAM limited by hardware, and a GT-330m that goes dark from time to time. If I want a better base hardware, I have to throw everything away and get a new one. What will happen to the great screen? Will they melt the aluminium case? How much an equivalent notebook will cost?
I really applaud the initiative, a buildable notebook is awesome. But even a standard motherboard within a manufacturer would solve so many problems. Get a great notebook today, replace the motherboard for a new one 5-10 years later, and keep the rest. Oh, that would be amazing. A nice step in the right direction.