I think it would be a lot easier to hack Windows Live to act like a System Link Xbox/PS3.
All you need to do then is connect the Xbox/PS3 via LAN or xlink kai and Select System Link.
(Well i'm not sure now... Does the PS3 version has Systemlink?)
This is only theory but seems like an good way to me.
A lot easier then editing game files on the Discimage.
The Teknogods Team is Modding the Windows Live Engine since Years. Maybe they can help.
They already modded GTAIV in a way so you can play it over VPN. TeknoGods.com - View topic - TeknoXlive 1.0
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