The new type of axle and tyres save 18% weight in rotating unsprung mass. I think this is a clear significant improvement.
Andy Murray talked about the setup for different conditions in the E4 presentation video, he considers diff remains only for really low grip. For this the diff is kept available. For hand out tyres the spool with 3 screw mount is kept available. Watch yourself:

I wonder, why a carbon chassis would be preferable in low grip. Aluminium is more heavy and lowers the center of gravity, thats why it is used in my opinion - this should not hurt on low grip too. Advantage of carbon is that you can use heavier RC components and still keep the weight limit.

Best regards, Erhard