Is it possible to generate a mesh for the map with only the outlines?

Can overlaps be removed like they did it in http://www.futurlab.co.uk/inside-velocity-2x-map.html
And how is it done?

Hello Wenturi,

I answered a question a few months ago that involved a tron glow effect around the edges of a mesh. You could adapt this tutorial to allow for your needs. You may have to use 3D assets to create your world as opposed to painted planes using this method.

The tutorial is in this users first comment. Let me know if this is a viable solution for what your project.