A family that I know, who live in the country, had started to re-do some of their house. They found a lot of dry rot the farther they went. By this time,there wasn't much house left, besides the concrete slab.
They decided not to spend the money to break up the concrete slab. Instead they decided to install a raised foundation on top of it. They talked to a professional and he told them that it would be a good idea. He gave some good reasons why. The house would look bigger, it would be easier to get to pipes and wires, and water would be less likely to get to the flooring.
If they needed repairs, it would be much easier to get down under to get to pipes, etc. When the house was finished, they were very satisfied with it.