There are some things to consider. Why does someone want a "working" dog? Do they plan to actually work the dog? Do they know what a "working" dog really is? Some people use it as a buzz word or to try and make a puppy sale. The truth is a true "working" dog has a high prey drive. They are go go go constantly and definitely think outside the box. So if you really really want that, then realize what you are asking for. And it takes a certain type of an owner/trainer to properly direct such a working/prey drive. Just like not every breed is for everyone. Not every ability is for everyone.
Boxers typically have a high prey drive. Obviously some dogs are more driven than others. But their pedigree does NOT make them the dog they are. And a "working" dog does not have a healthier genetic make up simply because of that designation. Every Boxer is different.