The trouble now Colin is we would have to import foreign made steel, then build shipyards to build ships and yes train people in various trades to build them. But more importantly find the necessary people and train them to man them. Since the 1980's the political will was call centres not manufacturing and getting foreign money in to capitalise our business albeit they usually left after stripping out all the research work and selling off the assists. So where is now the skills to do what you want, we even now import ammo, and aircraft.