everything shares one heatsink
everything shares one fan
Yes, how viable that is remains to be seen. According to the website, every detail of the fan down to the exact shade of "generic charcoal black #156" it's painted with has been hand-picked and carefully selected to provide the best possible performance.
Also: I just want to distinguish, the only original thing apple did was actually make the case. They took top end components from other independent manufacturers, none of the components were made custom to fit the new shape. The true test is to see how many thousands of dollars you can save if you build a comparable PC yourself