While this is a bit extreme, I just know there are ATLs out there where people on the local equivalent of AH.com are dismissing as ASB the idea that you could dig a canal through Panama...
Yes I agree, through I still think that the project are likely to be given up halfway, which are going to be a lot more interesting than finishing it, because it would create a giant freshwater wetland with many large artificial islands and great dykes which would also have rail and roads on them, suddenly it would be a lot easier to travel from one side to the other of the North Sea. While a disaster for the ecosystem of the North Sea, it would create a enourmous biodiversity among wetland birds and freshwater fish. Of course this wetland would also be a lot more peaceful than the North Sea making goods transport cheaper because of barge would be the main transport vessel. We would see Germany, Benelux, Denmark and UK grow a lot more economical integrated.
I imagine some of the first area which would be changed would be the Wadden Sea, which would become farmland, split with canal which would make transport easy. The Dogger Bank also lies inside the Dykes, so this would likely also be a important early target for reclaiming. Most of it except the westen third (which are closet to Denmark) seem to lay in English territorium and maybe a little in south which seem closer to Netherlands. It could be interesting if the new reclaimed Doggerland was split between Britain, Netherland and Denmark. It would give the three countries a land border. The northen coast of Doggerland would also be the the Great Dyke, which would mean the island would become a transportation hub for train and road traffic between Denmark and Britain.