Star Wars: Republic Commando nearly had one of two very different sequels - following Order 66 or rebelling against it. Obviously the second lets you carry on being a hero, while the first immediately suggests some fun gameplay if you don’t mind being the out-and-out bad guys.
(The bloody handprint on white trooper armour is quite the look...)
Building up a fighting force from the very beginning could be an interesting hook for a series. In a non-shooter game like an RPG, this could involve making alliances, acquiring supplies and disrupting enemy plans as well as direct combative action.
On the flipside I’ve thought about mundane soldiers hunting wizards before - specifically wondering how the S.A.S. would react to that time Death Eaters destroyed the Millennium Bridge in London on the way to Diagon Alley.