While I agree with your general sentiment, I do not think I have any responsibility if my gun is stolen and misused. I dont want them stolen, I dont have stupid stickers on my car. I try not to go to high crime areas. And if I do , the gun comes with me anyways. But if someone breaks into my car, and steals a gun, then what they do with it is on them ,not me.
Neither Strong side carry or cross carry work well with seat belts, And a shoulder rig needs a jacket for concealment. And if I have a coat or jacket the pocket works just fine. I do like the magnet for securing the pistol while im driving, even better is a holster type gizmo like the one above. But they too have a problem of being exposed when pulled over by a policeman, an ordeal neither they nor me want to go through.
Generally , I just keep it in the holster on my strong side, and wait till Imreally on the road to put my seat belt on.