Could glue/epoxy a sensor right behind the centre mirror I’d think. It’s far enough from the defroster vents that it wouldn’t heat up quickly from the hot air.

You could do one of two things. First, a heated windshield like I believe some Landrovers have. It’s about $5000 to replace, last I heard, but it works. Second, a double pane windshield like house windows or some motorcycle helmet face shields. These work 100% of the time, but would definitely be more expensive as well.

Best car I had for window defrosting/demisting was a Ford Mondeo which had a fine-mesh heating element embedded. Super fast clearing. More expensive than regular glass but not $5000 by a long shot.

I had a Honda Accord with a cracked radiator.... It defrosted right quick, but idling it after it warmed up was very ungood. After the radiator was replaced defrost went back to normal.

You can get it for most Fords. It's one of my favorite features, and any car maker that caters to the more northern people should have that option.

When it's sort of cold, but not "ice on the car" cold, it works great as defogging. Way faster than waiting for the car to heat up. When there is ice on the car, you turn on the heaters and within a minute or two you can simply use your wipers to clear the window of ice.