Jane Austen gives us a slight picture of how Fanny and Henry might have been married, but this depended on Edmund marrying Mary. If Henry had stuck to his duty as a landowner, and avoided Maria, there would have been no scandal, and a strong likelihood that Edmund and Mary would have married, with hormones on both sides overpowering rationality. But what kind of life would they have had?

We know Edmund's income was £700 pa. Mary's fortune would generate about an additional £1000 pa. That would be a very comfortable income for living quietly in the country, but I don't see Mary being happy in that kind of life for more than a few months in the year. She'd want to be off to London, or maybe Bath or Brighton. That costs money, and in addition, Edmund would have to pay a curate to mind the Thornton Lacey church while he was away. Edmund would be miserable if they exceeded their income, and I think Mary would be pretty miserable if they lived within it. (Mary never bribed a physician in her life? Maybe, but she'd soon be wondering how to shorted Dr Grant's life.)

So Mary and Edmund would have a conflict of lifestyle and income, while Fanny would be left at home when Henry went philandering. Not much chance of happiness for any of them, although Henry would come off best.