Excellent post anerlich.
Not to mention that some people have said wing chun to be the 'three-year art' (I don't endorse this opinion, but it is a relevant one).
I was holding my own using WC after three years, against karate people and other kungfuers.
As for percentages Wing chun tao, I can't answer since it's changed over the years. Maybe for the first 3 years 95% wing chun and 5% aikibased arts (but sparring other styles), then 80% WC, 20% aiki, now maybe 55% WC 45% MMA (everything!). It's also impossible to say, because the intensity in MMA is way way higher than WC, even in my own-generated style of WC...