The first thing I got rid of was the dice, but that was because I knew I wanted cards before I knew I wanted it to be FitD. I spent a long time figuring out how to "map" the success tiers onto a poker deck, but the artifact of a deck of cards was something I was committed to. It's becoming more central to the overall design as I move through the process, but every so often I think wouldn't it be easier if I just stuck with dice?
Editing to add another item I got rid of, pretty early on: Death by Trauma. I'm working with a slightly different system of harm, and I wasn't comfortable with the idea that psychological or social trauma would be something that a character couldn't overcome. It means also figuring out a better way to handle trauma, but I'm pleased with the concept of characters learning to cope with their traumas, rather than letting themselves be overwhelmed to the point of involuntary retirement.