What is so strange, that John uses the law to open his gospel?
Don't forget he was writing to a jewish audience.
So to start with the law, and with all jewish thinking in mind, that the law is good, just, and everything described in psalm 119, it wouldn't be such a strange thing to me.
It would be stranger to have the word "Word" there, because for a jewish audience, it would render totally useless. it would be the starting of a gospel, of someone who didn't know what to write so he started with a doodle.
it totally has no meaning, if you start with the preconceived notion, that you are a jew, know nothing of Jesus, and start reading this gospel.
Remember, that God is not a God of mysteries.
Michael