We are not talking about multiple 0-100% cycles daily. The places where pilot programs have been run always left the car with some amount of charge so it can be driven, and you don't normally charge NMC car batteries to 100%.

Vehicle batteries have 8 year 100k mile warranties today, and those manufacturers who have spoken on this topic have said that utilizing your battery as grid storage will not violate the warranty (Ford said this about the Lightning, which can do V2G today.)

Please stop spreading misinformation and go do some research before you spout FUD like this.