IMHO, full foot fins are generally better than open heel fins. They are more efficient, more comfortable, and simply a superior design, especially for scuba. The only reason, IMHO, to resort to clunky open heel fins is colder water, when thick boots are needed. I often see vacationing divers in tropical locations using open heel fins, with thick neoprene boots. My assumption is that they don't own a good pair of full-foot fins, and so must adapt their cold water gear as best they can. How sad for them.
I think the suggestion regarding skin grafts is good. Really serious divers might consider having their feet flattened in a wine press.