The silhouette is beautiful. I like how the lower side sills flow into the aggressive rear arches. I don't particularly like the intersecting line on the door angled towards the front fender. It breaks the flow of the crease line from the hood to the rear. I agree it looks like a sleeker Z4. It has the same classic proportions of the first XKE.
As far supercar parts are concerned, BMW has more than enough parts to create a great machine.