I have a better idea, why not just drain the Channel ?
I.e. do the benefits to your country outweigh the costs? I suspect it would be very unprofitable, but I haven't done any calculations
Benefits would obviously have been greater if you didn't already have a tunnel, and wouldn't need customs and immigration checks.
There's a railway deck beneath the motorway deck on the bridge-part of the connection. The bridge is 8 km long, but then there's also 4 km artificial island, and 4 km tunnel under the sea at the Danish shore (where the car- and railtunnels are beside each other). And yes, the bridge has been profitable
Took 5 years to build it.