Your ideas make a lot of sense. I dearly love New Orleans, but it doesn't have to be rebuilt exactly in the same spot. It can be bigger and better than ever, but just in a location above sea level. The same could be said for the Mississippi Gulf Coast. Let's rebuild, but in a way that makes us less vulnerable to hurricanes. No offense is intended -- I just would hate to see something like this happen again the next time a hurricane targets this area.
With this plan, you can salvage the French Quarter as a tourist destination - it wouldn't be that hard to keep it leveed off, since it is already near or above sea level. I doubt tourists went far into the areas currently under 20 feet of water anyway.
There is land to the west that is 20 feet ABOVE sea level instead of 20 feet BELOW sea level. And much closer to the future channel of the Mississippi. This shouldn't be a tough decision.