You would have to prove to this advocate of ID that the more improved design would indeed be an improvement or complimentary to the overall design. In other words, are those claims potentially falsifiable?
Sea Mammal Blowhole. Any animal that spends appreciable time in the ocean should be able to extract oxygen from the water via gills.Enlarging the lungs and moving a nostril to the back of the head is a poor work-around.
Mammals have faster metabolisms than fish. Gills are apparently insufficient for mammal metabolism. Link provided here:
In fact, I have read a report on biomimicry that reported the following:
Dr Frank Fish, an expert on how animals move, based at the University of West Chesterfield in Pennsylvania, was looking at a sculpture of a humpback whale, when he realised that the artist had put bumps on the whale's flippers. That made no sense: everyone knew that the leading edge of a wing had to be smooth and streamlined.
The gallery owner, however, assured Dr Fish that the bumps were in the right place. Intrigued, the doctor made a thorough investigation. What he discovered was that the mysterious bumps were precisely the right shape, and located in precisely the right places, to make even an animal as cumbersome as a whale extremely agile, as the bumps produce vortices that generate more lift and reduce drag.
Can't digest cellulose which makes up an appreciable part of the human diet. Since cellulose makes up a large parts of plants which are eaten by many animal species and the others eat animals which somewhere back in the food chain,
Once again, I would remain skeptical until you could prove that a human would benefit from digesting cellulose. Cellulose apparently serves another purpose. It is a fiber and serves as helping move food through the digestive tract quickly and efficiently.