M$ is making the SAME mistake they did with the first 360 design.
Assembly it outside of the case, use a couple of good fans, run the machine non-stop testing stuff.
They really needed to assembly it into the final case, with fans they pick for shipping, and play some games, turn it off, wait a while, play some more games, turn it off, wait a while, play some more games.
Because during later eng. tests on the RROD problem, it was total amount of "thermal cycles" that kill the 360, around 2000 thermal cycles some problems, by 2500 cycles more problems, by 3000 total failure on all machines under test.
Oh'well. -- As for consoles, both the PS3 and 360 from day #1 have used 2.5" SATA hard drives, so that is not the reason for their "biggest" -- You could go the Mini-Blu-Ray way, have 7.6gb mini 3.5" blu-ray drive! -- Would make it smaller! -- But really in today's world, why the **** are we still using HDD and spinning discs, just use a 64gb solid-state card, that is bigger then even a blu-ray disc!