I don't know what xbox 360s you've looked at, but they have standard USB ports.
The controllers use standard AA batteries.
If you're so gung ho for open, maybe you should consider the console that makes use of standard AA batteries.
And that whole hard drive thing, long over.
The 360 can use any USB mass storage device for game installs, save games or media.
So the PS3 can take any garbage hard disk but cannot deal with AA batteries in it's controllers?