I’ve never done exactly what you are asking. I think it could be done using custom XSLT.
If you are not an expert XSLT coder (not many of them), you could always pass the message into a .net component inside an Orchestration. Then, you could use any type of logic you wanted to sort the message and break it up. It wouldn’t perform well though and if the message got to big it would “Out of memory” on you.