Can the stock side mirrors be converted to defrosting mirrors?
Can strips like the ones on the rear window be added to the back side of the mirrors then connected to the defrost switch?

My side mirrors defrost. When I hit the defrost button, the side mirrors get defrosted as well as my other windows.

I'm not sure if it's just a feature that came standard on my GLE. Maybe you could swap out your side mirrors with ones that defrost? Not exactly sure how the defrost feature works on my side mirrors.

Hope this helps and good luck.