I really don't think that cannibalism is as big an issue with these frogs as people think. I have never witnessed nor heard of cannibalism actually happening when adult or even subadult specimens are concerned, and I have seen pretty huge size differences kept together. I really wouldn't push it with keeping a female dwarf and a male adspersus together, but I don't see why these species couldn't be kept together. I would be willing to bet that interbreeding could happen genetically speaking, but physically, it would be impossible. These species have such different methods of reproduction that they really would not be compatible. It would only happen if somebody used manual fertilization.