I prefer clean designs also, and the fact that I'm using a CM Storm Sniper as my current chassis makes me feel a little strange, haha. If I could "upgrade" the chassis on a dime, I'd go with something like Corsair's 700D... it's just ultra-clean, and super classy. Like its fan controllers, NZXT has never really made it a point to create chassis like this, although the Adamas might have come the closest.
I love your idea, a <em>lot</em>. A clean design fan controller with monochrome colors (gray and white, or something like that) would be fantastic, and easily better match up with some of the cleaner chassis out there. I'm not sure about its face though... mesh is one idea, but not all chassis use that. I think a brushed aluminum would be nice, but again, not all chassis have that either. It almost seems the best way would be to include two swappable faces or something, and let the user choose between them. It's impossible to produce a product like this that will suit everyone, but I think both a black brushed aluminum and mesh face would take care of the majority.
Either way, whether a less-color fan controller comes to fruition I'm not sure. NZXT clearly dedicates itself to gamers, but even then, people who purchase clean chassis can still be gamers. It will be interesting to see...