What does it mean to "seal" the marriage?
If it's signing the license (document) after the fact, then won't they just contract out to some third party that can sign afterwards?
Or if "sealing" means conducting the part of marriage in which vows are exchanged, then I can see the elder doing the normal wedding talk, and then some third party contractor gets up and says 'Do you? Aaannnd do you? Etc'