I will admit to being even further unqualified to comment and say that I've never seen Batman and Robin, but even if you could make it better by making it funnier, it's still going to be a different story than Dark Knight. And, again, it all comes down to what you think is essential from the source material, and if a funny Batman doesn't capture that for you, then it's not going to seem like Batman no matter how hard you're laughing. Some people like the Dark Knight dark, you know?