While engineers are working on the easy part (the tube map), I've already developed signage for some parts of the system (shown below). When I return from London, I'll try to set up a meeting with Governor Richardson, who made the current rail system (fabulous but limited) a reality.
If this plan doesn't fly, we can go to Plan B: put tube signs in all towns so it looks like we have an underground rail system. That will encourage people to visit when they see photos or tourism ads that include tube signs. T-shirt and coffee mug sales should cover the cost of the signs.