U don't know what you are asking.
Even desktops they don't let you change CPU. GPU, memory, some upgrades OK, but it only takes u so far, before you have to change the whole box.
This concept is been around u know... There were computers that everything are on plug-in cards, including the CPU, so theoretically u can change everything. The "chassis" is just a bus for everything to he plugged in. Problem is, after awhile, the BUS is no longer sufficient it no longer provided the bandwidth for the upgraded components, so again, start from scratch.
Sorry to burst your genius idea.