Even if it all works out, and you get all the things you want out of the relationship now, and amicably divorce later, there are still lingering issues. Anytime you apply for a security clearance, you’ll have to disclose this marriage and he might have to be interviewed. If you can’t locate him it might cause a delay in your hiring. Any time you register for a license, be it medical, law, etc., you’ll have to provide information about the marriage and divorce. If you want to adopt a child, you’ll have to provide the documents, sometimes certified, apothocated, or anything else they want. It’s a pain and it costs money for each document. What if you want to run for office? It will be one more thing to overcome.
It also might cause personal problems for you if you want to be married in a church in the future. That would be your own decision as to whether it will be an issue.