an interesting spin to add, is the documented suggestion that some forms were created for aesthetic value only. Have a read of the compilation of Chinese Training Manuals by Brian Kennedy. also the book on turn-of-the-20th century Chinese sport programs by Andrew Morris.
It's reported that some forms were composed with a sortof street-performer advertisement mindset during the 19th century. and during the 20th, forms designed specifically for athletic and dexterity exercise.
The aesthetic: Body movements to interest and attract for recruitment into schools (which often doubled as political movements during the various insurrections in Chinese history).
The physical: China (and many Asian countries for that matter), sought to beef up their physical ed. programs during the turn of the 20th century. as they engaged the world arena, they saw how their social stuctures were lacking in the area of phys ed in schools and culture. With added programs and much propaganda, they turned that image around.
so it seems, tracing back to older forms do not, by definition, necessarily bring you closer to your goal (assuming your goal is extracting fighting principles from traditional kata of Chinese origin).
Does your kata come from an Okinawan, who learned an aesthetic Chinese form and perhaps changed it to attempt to meet his needs and abilities during his time period? or is the kata you have an exact replica passed down with effective fighting principles intact?
this thread's question is a double-edged sword: your kata could be a composition made from forms which had no 'application' or an application which is different from what you intend to use them for now.
In a way, you are retrofitting your intent into a kata, in order to exctract your intent....which is a self-fullfilling prophecy. I'm sure you'll find exactly what you were looking for and claim kata-based training a victory.
An excellent argument to address: why not just train your intent without the self-imposed baggage of kata? If you go back far enough, there must have been a time when there was no kata - how on earth did they learn how to battle?
and I would argue, the further back you go, the more hand-to-hand combat you'll find. so the birds-eye view moving back in time: more hand-to-hand combat, yet less kata. hmmmm.
...just thought I'd throw that log on the fire.