To me, it was broccoli minus the texture, diluted with salt water. I prefer the texture of the brocolli and full flavor of it. Now, part of the issue for me may be that I'm on a sodium restriction and so didn't season the broth with the level of salt to achieve Gordon's vision. But honestly, that's never been a problem with other recipes I reduce salt in and my taste is adapted to lower sodium, so I don't think that's it. This soup really only has one note to sound, and there are better ways to sound that one note.
I love soup. It's something I look forward to trying in a new restaurant, especially when it's an ethnic restaurant. I like the window soups open into a cuisine. I enjoy how soups marry flavors and accents. A soup should be a symphony of flavors. Sure, a symphony often has a solo artist which makes a special performance, such as French Onion Soup, but the whole result is more than just the solo.
Now, I think this soup shows a lot about Gordon's approach to cooking. It's fast. It's simple. Very reproducible. It would work well in a restaurant setting where you can go from start to finish a few minutes. Great for a first course. You see the same approach in his programs like Kitchen Nightmares or Hell's Kitchen. Similarly, I think it targets an audience without the deeper understanding of food.
I don't think it needs to have dairy or be a cream of brocolli to be improved. But it does need some aromatics.
If I did it again I would add some butter to finish it, probably a compound butter. So there's me giving in to some dairy.
I think there's the potential for an interesting Asian influenced version. Ginger, garlic, fermented black beans, a little Shao Hsing wine and an asian based stock. Or even with oyster sauce and ginger and garlic.
As to what else you could do this way. Carrots, though they need more cooking time I think. Zuchinni, though I'd deseed them first I think--I'd probably go with a saute in butter first to concentrate the rather weak flavor, then puree in a mild vegie stock. Many butternut squash or bean soups have a similar simplistic approach. Sweet potato has potential. Nick Stellino does a pureed potato soup, heavy with garlic that's quite nice. http://www.nickstellino.com/recipes_display.asp?ind=436 Most of these need more time though.