The US does this all the time.
For example, the Navy LCS program called for a fast ship that could patrol the coastline while traveling as quickly as a speed boat. Lockheed Martin designed the Freedom Class. They made a 378ft, 3,000 ton boat that can travel at speeds of 47 knots, or about 54 MPH. However the Navy was not very happy because they concluded that it wasn't survivable enough and that its armament was lacking. These are all things that should have been well defined at the start of the project. Especially considering that the speed requirement practically begged designers to make certain compromises in order to limit weight.