As Stated Before.......................
In my opinion and observations thus far, the only purpose that spirituality has played in the martial arts is by giving its' practioners a sense of purpose or specfically a "Holy" purpose.
Zen Buddhism, Taoism, Confucianism and the like... were all a great influence in the martial artist because of the times. These were the major religions in China at the time. If martial arts was developed or prevalent in the US, Kung Fu might be a little different, with a more western or White Protestant type logic to it. If it was developed among natives, it would have had more of a naturalistic or anismistic type of philosophy.
Meditation is done in many religions in different ways to achieve the same end, As the goal of all religions, spiritualities, philosophies and thoughts. It does not improve the Kung Fu, it improves the individual that practices it. There have been devout excellent martial artists with unending legends of their skills and devout devotion to mankind, just as their are legends of excellent martial artists that have killed, robbed, raped and terrorized people.
"The key is to begin at the beginning;high level short cuts can only lead to dead end."
"If You can't be honest nothing can happen."