Gosh, I bet that would make a pretty killer gratin if you thinly sliced and layered the celerty, fennel and cauliflower, then used sauteed leeks in the sauce. It would look an awful lot like a potato gratin, but be so flavorful.
I agree - saw this list and immediately thought gratin. A Gruyere would probably be nice, add a little thyme and a little sliced marinated artichoke heart and you should have something pretty spectacular.
Love the Gruyere but would hate to see the flavor of the artichoke hearts cover up the pretty subtle flavors of the others...the marinated ones I had recently were too vinegary and really overwhelmed the dish I used them in.