Given that each element in the five rings represents multiple things: It represents the actual element, the philosophies behind the element, and on top of that, physical and mental strengths that revolve around the element.
Let's look at Water, for example. Water, in the d20 system, is, as a score, based on the lowest of your Strength and your Willpower. This meant that Water shugenja were quite capable of imposing their will, physically AND mentally. It wasn't just 'They get some spells that get things wet' but their chosen elemental focus went deep into their capabilities.
Not to mention, Water shugenja weren't by happenstance; only three schools were teaching the ways of water: The Lion clan's Kitsu, the Unicorn clan's Iuchi, and the Phoenix clan's Isawa. Each had a different inherent philosophy involved as to which aspects of water they teached: Kitsu magic tended towards ancestral communion, Iuchi magic tended towards mobility and teleportation, and Isawa's was focused more on the general capabilities of water itself.
This 'fluff' actually expressed itself in very crunchy ways, in that each school had signature spells the others couldn't get, or in the case of Isawa, limitations the other two had simply did not apply. Combine that with the family itself; every family you could belong to had its own mechanical bonus to represent your heredity. An Iuchi-schooled shugenja usually was Iuchi born, but a memeber of the Moto might show some skill with the mystic arts. This would indicate a shugenja with slightly different stat-bias. Even the same clan sometimes had different kinds of shugenja: A Scorpion clan shugenja could be a Soshi-family, Air Shugenja, based on trickery, guile, spying, and information, as to investigate the enemies of the empire, and the clan. Or they could be a Yogo-family, Earth Shugenja, instead focusing on counter-magics, wards, shieldings, and ways of blocking and countering evil blood magics.
For someone who complains often that 4e tends to have little mechanical-fluff connection, I'm actually kind of surprised that you'd chalk down the Five Rings of Legend of the Five Rings down to 'mere fluff.' I think you're really cheating yourself out of a fantastic, flavorful system. The Five Rings determine every aspect of the game, from how magic works, to even how the books are laid out. (Hint: In five parts, each element representing a different part of the presentation)