Okay, after molesting Siri's files a little, I found a little entertaining something. Go to Springboard.app and locate any random language folder, e.g. English.iproj. Edit the Assistant Strings file at the line "Assistant_Not_Available_Title" and "Assistant_Not_Available_Subtitle". You will get something like the pictures below. Wonder if someone can help me make a tweak that allows you to change Siri's strings? Okay, the website is not valid, but it is meant to be 1) a joke and 2) a wild goose chase for less intelligent beings.
You could always change all .strings files to your liking. People have made some tweaks for changing the biggest ones such as "slide to unlock" but I don't think it is necessary to make tweaks for all of them when you could just edit the file.
