Observations :
1 : Some public libraries (and many college campuses) now have Makerbots and similar 3D Printers available for public use at a nominal fee. See also : Fabrication Laboratory. I haven't done the math on a Lego-compatable brick, but a meeple of plastic costs 1/4th the price printed at my library as one ordered off gamecrafter (1/3rd if you buy in bulk)
2 :
www.TickerCAD.com offers free, light weight, web based milling / extruding file creation tools for use with such machines.
3 : As of 03 March 2015 the Wikipedia.org website's entry on "Lego" includes the metric measurements for standard and thin blocks. (See also
http://en.wikipedia.org/wiki/Lego_clone for issues and historical precedents involving legality of producing such bricks)
If you're a non-purist I don't see why you couldn't make whole mech components single printed pieces with appropriate attachment vacancies / extrusions.