[jzampier]

Here's how this would have to work:
(I'm working with USB for a senior project.)
USB is a serial bus. This means that it has 2-way data communication over a balanced signal. The usb connector also happens to have +5 and GND.

I'm assuming that the XBox controllers have some kind of 'smarts' in them to multiplex (that's assemble) the button pushes into a serial data stream for the USB. So, first off... they require power. I wouldn't recommend trying to draw power off of the OI joystick ports without talking to IFI about current limits, which I don't think are published as such. Secondly, since you aren't allowed a 'computer' at the player station ... well, you can see where I'm going with that.

Now other issues aside the techy details...
A PIC18F4550 appears to have USB support and is in a PDIP package, which means you could actually solder to a IC socket. (It's not a surface mount)
Then you need to write the pic code to decode the probably custom data stream from the XBOX controller and demultiplex it into a set of digital outputs. Then you need to D to A the outputs for the analog sticks because the pic doesn't have built in D to As.

Now how I would do it:
I'd disassemble the xbox controller and see what's inside... I'd try to re-wire it so that each of the buttons has a direct output line to a DB-15 connector.
I'm rusty on my rules, but I don't think you are allowed to do this. (Check)