Basically I believe the difference between ancient dynasty swords or swords that will be use by soldiers in real battlefield (all the way down to WWII) as compare to kungfu sword (Taichi sword) was that the blade are normally thicker, slightly curved at the front for quick and fast drawing of the weapon and the blade is stiffer as compare to normal Taichi sword.
Sword unlike what many kungfu techniques had said that they are for piercing and stabbing, but I believe that the sword used by soldiers in ancient dynasties are mainly for hacking and slashing. Soldiers doesn't need to be extremely well trained in Taichi and other kungfu... they need to be able to be deploy in the battlefield quickly in Chinese context. Qin army was among the first to use conscripted soldiers... who basically do not really have extended training in martial art.
So what is more useful to farmers and other commoners when throw into battle? A weapon that is heavy enough and easy enough to use against opponents and what is easier than slashing and hacking your blade around blindly.
You basically described the so called Kung Fu broadsword. Although broadswords became part of the Kung Fu art, its original intention wasn't like that. They were made by counter Qing revolutionaries to train farmers and peasants as they were easier to use in slashing attacks compared to the Qing type sabre daos that require quite a bit more training to master. In the battlefield, the broadsword made quick chopwork of the Qing swordsman. Likewise, the Qing got the idea as well and used the same.
On the first paragraph, what you said about hacking and slashing is partly true...and false.
During easier periods and this also happened with the Middle East and Mediterranean, sword metallurgy wasn't good enough for hacking and slashing. The result of trying to do that would result in broken swords. Plus slashing is easy to parry away with a shield. At that time, swords are fairly short because of metallurgical limitations.
So what's the strongest point of the ancient sword? The tip. The thrusting attack is actually the most sturdiest attack and the one most likely to break through armor. Why? Because you have the entire length of the sword reinforcing the tip from top to bottom. Where as a slashing attack, you are more likely to break the sword.
So guess what. When it comes to slashing attack, the best weapon then would be a pole arm. Especially if the tip is lengthened so the whole blade reinforces the tip. Now you're looking at the design of the Ge, which is why this weapon is remarkably efficient for its time.
Swords became hack and slash the moment the metallurgy became good enough for this: the sanmei construction, folding and layering, use of carbon steel. But at this point, when it comes to hack and slash, the dao or single edged sword, proved to have the advantage over the Jian, whose use decreased except with officers and more seen to signify status. Instead of being used in war, the Jian increasing became decorative and used with exercising and training. The analogy today is the officer's pistol.
From the Han Dynasty onwards, swordsmanship in war becoming more dominated by dao and with two hands on foot, and single handed on cavalry. Also, with cavalry troops, dao is also preferred.
The relationship and transition of Jian and Dao is an essential part in the study of Chinese melee weapons.
It should be noted, some of the best surviving ancient Chinese dao are actually preserved in temples in Japan.