Best 'All purpose' lens for weddings? (Nikon d7000)?

I have been doing weddings and other portraits lately with my Sigma 17-70mm f2.8 lens and it has been great, but now that I'm getting more business and more weddings I would like to upgrade to something better. Something between the $1000-$1500 price range, I want a lens that I don't have to take off the whole day. I have a Nikkor 50mm f1.8 but it doesn't work with my flash, so I don't normally use it for weddings.

How about this?

http://www.bhphotovideo.com/...200mm.html

Daniel has a good idea.

If you really believe that there's an "all purpose" lens, I would never hire you to shoot my wedding.

And if you are only bringing one camera body or don't know how to use a 50mm lens with a flash, I also would never hire you to shoot my wedding.