Breatheability would be an issue with me also. When they shrinkwrap my boats, they always leave vents so that any dampness can evaporate. You don't want to trap any moisture in there. I think most of the covers are intended for temporary outdoor or overnight storage. It doesn't say in your post but I'm presuming that you intend to keep the car outside. Protection from the sun is a must.

If you can afford it I'd go for indoor storage. Ask around, you might find a co-worker with a mom or grandmother that has room in their garage because they no longer have a car and could use a little extra money. Just throw a sheet over it to keep the dust off.

My two centavos