I can only think of one weakness in the design of a 1911 pistol. If you push the pistol until the end of the barrel contacts something it will unlock the pistol and it will not fire.
As will any semi-auto with a proper disconnector.
FWIW, this can be overcome by holding your thumb against the back of the slide enough to keep it in battery. It obviously won't cycle for the second shot, but if one shot can help you create distance off a bad guy you can clear the malfunction and keep working.
An exposed hammer would complicate this, so that seems like a pretty objective potential weakness of the 1911s exposed hammer......In a scenario that has 1/1,000,000,000 chances of happening.
