First, we've updated those instructions to allow the use of more recent MultiChain protocol versions.
I'm afraid we don't yet have concrete step-by-step suggestions on how to do this, beyond what is written on that page. But if you stick to non-asset transactions the wallet should be highly compatible with minimal changes.
In terms of streams, you would need to add functionality to the to read data from the stream. You can use the bloom filtering in the bitcoin p2p protocol to detect patterns of the stream data, which is formatted as written here: