Well... I don't really know anything about writing scripts, but seeing as how no one has even tried to respond to you, then I will go out of my way to see what i can find...
"Searching google".... "Search complete!"
It seems that IGN posted an article for people who want to make XBLA games. It doesn't say much other than if you really, REALLY are serious about making a game, then you can actually contact the Arcade team (Microsoft) with your game concept and then they will be more than glad to help out... However I realize that the article was posted 5 years ago and because of it, you might not get a response from the Arcade team so I'm sorry if doesn't work out but I really hope you have the best of luck with your goal!
Contact e-mail:
[email protected]
Article: IGN, process for making XBLA [http://xboxlive.ign.com/articles/721/721843p2.html]
Hope it helps.