A back sheath sounds good to me. Much better than pulling the gun out of thin air. Or it could just be slung over the shoulder like the trooper's rifle. I mean, they animated the gun already for when you use it.

I just chose to be a scoundrel and was very excited to blast people with my scattergun. After equipping it I was dissapointed that it's invisable! My scoundrel reaches over his shoulder to grab nothing and then out of nowhere a long scattergun appears, blasts, then disappears again. How cool would it look to have my scattergun slung over my shoulder waiting to be unleashed. I mean, it's an actual weapon I equip, so why can't I see it?