Removing is easy too. Just remove any .C linkings(int update_ELEMENTNAME(UPDATE_FUNC_ARGS);) to the element. If it just doesn't react with other elements. Then leave the "#define elementname number" there and it'll be OK. Also you'd need to remove the element description from the element struct.
Bubbles are just loops of connected particles, no more, no less. It's not step to movable solids, not "try of technology" or so. I even doubt that there are going to appear more elements using connections like in soap.