All systems of martial arts must evolve, if not they become stagnant. Now take this example in regards to striking. Boxing is considered by many a very effective style of striking. There are four basic punches in boxing- jab, cross, hook, uppercut. There are variations of these and several different combinations, but these are the four basic strikes.
Pretty much all of these you should be able to find in any Kung Fu style, they may have a different name but they have the same mechanics. Now take into account the delivery system and how these techniques are trained in regards to their effectiveness. A boxer can throw a jab and crack someone with it because they have thrown it hundreds of times before on a heavy bag, on mitts, and while sparring someone. If the Kung Fu player has a similiar approach, he will be able to do the same. If he has spent more time posturing, punching air, and performing this jab while doing a form, chances are his delivery system and his ability to use it in a pressure situation went down significantly.
This would be an example I believe of style evolution if you want to call it that. The system already contains the technique, so it's not something added or newly learned, simply a change in delivery system or training method to make it more effective.
Now this can work also for other styles in comparison to Kung Fu. TCMA are for the most part very rooted systems, meaning stance training is an important foundation to build upon. Leg strength and transitioning ability is gained through proper stance training, and is very important for other styles, particurarly grappling. If I am clinched with an opponent and have under/over hook on their arms and they are pushing through and powering, dropping the weight into the front leg similiar to bow and arrow stance and upshifting your weight onto the underhooked arm will throw them off balance, allowing you to follow up with a throw or strike. The movement and dynamics of rooting is what is important, if you want to chop down a tree you start with the trunk, but if it is too strong it will stay uprooted.
I believe people are way into what they believe are "pure" systems, when in reality TCMA, just like all other systems of fighting, are systems put together from various techniques and "training methods" that were developed through trial and error and combat testing. The masters of old would have gladly learned new and improved training methods to deliver their techniques more effectively. Why some here in modern times can't or won't I will never know.
"The hero and the coward both feel the same thing, but the hero projects his fear onto his opponent while the coward runs. 'Fear'. It's the same thing, but it's what you do with it that matters". -Cus D'Amato