I know they've since made droid commandos, but at the time this was my answer to the CLone Commandos. A Commando Droid that shared a body with a SBD, but had advanced weaponry, tactical programming, and thick vibranium armor. A solo threat to a garrison of clones. Obviously Lucas liked the idea of elite strike commando droids as he used it three years later in the clone wars. Each with a slightly unique paint job no less.