I'm not so sure you will have to suffer God's punishment for having this opinion; this has really been a "gray area" for many Christians. In the Bible, the dad or his servant brought the prospective wife home, he took her into the tent and consummated the marriage. Done deal. (Just think how much was saved on the rehearsal dinner and wedding.)
But, having said that, it is plain from The Scriptures that there were certain laws, customs, ceremonies, etc. that determined that a man and woman were legally married. I could cite numerous Scriptures but no time or space to do so. Bottom Line: I think that we must "render unto Caesar what is Caesar's and unto God what is God's." (Matthew 22:21). Why not just do it right and have a clear conscience before God. The Marriage License isn't that expensive.
As I said I do not believe that a legal marriage is necessary without children.
But she still tossed the bouquet before entering the tent, and that made it official.
Jewish marriage customs are very interesting and I don't think they've been captured in these posts!