That changes the meaning quite a bit--in the original, the word "suppose" was used in the sense of an obligation; in the new sentence, the word "suppose" is used to mean "a guess".
If you're saying that I was being passive aggressive, that's my bad, because I was aiming for over-the-top bravado and didn't go big enough for it to be funny, I guess. http://dilbert.com/strips/comic/1995-06-24/