1st- Make an entirely new chipset, not a mod of the current and failed chipset, so that the RRoD isnt such a usual problem(that or hire new engineers).
2nd- Big HDD and bluray on only 1 Xbox(It wont be necesary to overprice ur hardware with #1, ur warranty budget will dramatically drop, and it wont be necesary to have 2 Xboxes since #1 and #2 will make ur Xbox cheap and this time u wont lose $)
3rd- Optional Avatars( nobody likes them)
4th- It WILL cost even less if u make it smaller and quieter
Thats all I would want in an Xbox and then I will buy it. I dont even care about the 8800 chipset( even though all the swarming trolls in this article will care with the bias and all that). I think Im WAY overdo to play GoW2 and Halo.