It's a long shot, but you never know. First, cast your eyes towards this TF2 update page, and then to this official post on the Team Fortress 2 website.
Quote: "The Saxton Hale Mann CO brings you a brand new product for RED and BLUE corporations: the GUARD DOG. It's a multi-function class working either as offense, defense and support. The hanger is Guard Dog's primary weapon and uses two triple-shooting cannons. Despite having a manacing look it's weaker than it seems, but it's still useful to keep unwanted guests at bay!
Its a fake (and bizarrely well thought out) update made by a fan, and the Saxon letter is simply Valve's response to it.
Besides, the class is so similar to the Scout if the wanted to implement these changes, they'd just give it to the Scout. No need for an additional class.