Some interesting insights into what challenges the designers faced for W08, the diva.
Link -> Why Mercedes was so confused by its diva
Mercedes chief designer talks about having designed a 90% car for 2017 and not a 100% car. He further elaborates, the car wasn't 100% optimized on all grounds and they had let a lot of space on the car to handle unknown challenges of new regulations. They also had a late change on the PU side, which they could accommodate on W08 as that philosophy helped. Had that happened on W07, they had to completely tear down the design to accommodate it.
They built a lot of adjustment into the car, the capability to react to things that they would see. He says, unfortunately most of the things they had to adapt to, they hadn't seen coming.
Now that they understand the challenges of new regulations and the problem areas of the W08, he says, they can be aggressive with next year's car.