This is a terrible idea honestly
Fiora is more than likely to get nerfed throughout the next several patches, creating an item to nerf a champion is bad balance decision because the champion is going to be nerfed anyway and now you've possibly created other balance problems.
If you are a tank in a teamfight getting ulted by fiora all you have to do is... run away... if she seriously dives you so hard to try and pop the vitals your adc should be able to kill her EASILY, you don't have to worry about peeling because... you have been chosen to be focused anyway?
If you want to 1v1 fiora on champions you shouldn't be able to, then you need to either be playing a champion that scimitar is good on. or have determined the win conditions rely on you being able to 1v1 her and thus you need to put up with an inefficient gold item.