Yeah i don't see them bricking the console either. They could have the console not boot up with the hacked firmware in place like "FreshOuttaMaps" said. Then all you have to do is restore the original firmware and you're good to go again. If you go on Live with the hacked firmware then it's your fault if you get banned, plain and simple..
MS owns the code in the console. It is ILLEGAL to tamper with, reverse engineer, and modify that code. If you do so and the console does not boot, regardless if it's from a firmware update or not, then it's your own fault for tampering with it. Read the legal disclaimers that come with your Xbox 360.