There is nothing more sexy than raw power.
I did not like the tumbler, but at least it appeared more serious than just about all Batmobiles that had gone before. This is a real-worldish universe these movies are in, and so the new Batmobile makes sense AND is aesthetically pleasing. I am sure they will modify it, but they really dont need to.
With that said, Clayface seems like an odd choice if these films dont want to depict metahumans. Thats his whole thing, being able to reshape himself. Take that away from him, and you dont have a whole lot.