Hacking the XBox Live software won't get you far at all. Possibly looking at rewriting a good portion of the code (probably all of it). And still, you'd still need a T1 or better (depending on the amount of ppl you have playing at one time) if you are talking cross town or cross country. It'd be easier to just stick with tunnelling software for right now...besides, if someone did by chance find a way to make (or emulate) their own XB Live server, they'd be very hush-hush (if they were smart) about the whole thing.