I have had dragon wrasse's in my reef tank on multiple occasions. Easily one the coolest fish I have ever had. If this is something you want to do you need to get the dragon wrasse really small an inch or two at most. Be aware once it is about 3 to 4 inches it will start moving everything around in your tank, also may start eating hermit crabs as well.
My advice if you want to keep a juvenile in your tank for a year or so you can, but it will get big, dull looking and destructive very quickly. Really shouldn't get one unless you have a plan on what you are going to do with the fish after it becomes a sub adult / adult. Turning it back to the LFS is kind of mean in my opinion...