The renderings below of what would be a production 435i cabrio look beautiful. The 4-Series does look good with the top dropped. This appears fairly close to the real deal but the front bumper LED's may be missing the mark as they seem to just be copying the 4-Series concept car. The rear is likely spot on.
The question becomes, how much weight will the folding hardtop add to the 4-Series? If BMW can keep it down without the large increase the previous generation E93 saw with the folding top this looks to be a winner. Picture renderings below.