Agreed. Another thing to consider is that years in an art doesn't equate to skill in that art. If someone trained in an art for five years, 3 times a week most weeks, while practicing at home, and someone else went once a week, often missing multiple weeks in a row, and never practicing at home they're going to have vastly different skill levels. But if both are writing a bio, going by years, all you'd see is both instructors have trained 5 years in X, at the same place.There just doesn't seem to be a good answer, does there? (If all of the arts got together and said "We will all have black belts and it will take this many years in all of our arts it would be different).
I'm hoping someone on here has a better solution, but I think ultimately, you'll have to sacrifice to either appeal to existing martial artists, or appeal to the masses.