I had a Noah fabric full car cover that fit over the entire car and had elastic at the bottom that kept the cover secure. (Think of putting on a fitted bottom sheet on your bed.) The inside of the cover had a soft fabric and, on an Arctic Silver car, I never saw any sign of wear or scratches (but of course the car must be clean when the cover is put on). Mine had the provision for a steel chain with lock to attach to some grommets for added security but I never used it and I suppose that the cover survived some significant storms in the 5 years I used it. Even had special pockets for the outside mirrors which I suppose added some security. Came with a bag which it fit in when folded and stored in the frunk.
In the summer, the Boxster got the garage, in the winter, it got the cover and parked outside.
www.calcarcover.com was where I got mine ($225 now) but I'm sure you can find something similar over there. It survived significant snow and ice storms over a 5 year or so period and was perfect when I sold the car. Was so durable I'd use a push broom to remove a foot of snow from off the cover and then go drive the car the minute the streets were warm enough.
New switches can be bad and the electrical portion can be installed slightly misaligned to the mechanical portion.