I said remake the original with this level of CGI, as it would be a cartoon it wouldn't be impractical.If you check the trivia in IMDB it gives a couple of good reasons why megatron couldn't transform into his gun alternate mode. For the toy market side of things some states in America have made it illegal to make toy guns and this would have caused problems. Also it was just impractical have the big bad guy turning into a huge pistol and having someone else shoot him. I thing Megatrons transformation was the best in the film, megatron jumps up, clink, clank, clonk, woosh and off he goes. Clearly the decepticons know more about style than the autobots.