I have no idea whether this will go anywhere. But I wanted to suggest something in case a few somebodies with engineering degrees want to take it on. How about creating an open-source design for streetcars that any small municipality (or even well-funded hobbyist) can follow to bootstrap a system? Such systems -- think of the Kenosha trolley or the Old Pueblo trolley -- tend to inspire people to expand into larger systems, so this could be viewed as a way to bootstrap local mass transit all over the country. Some likely subprojects:
An open-source design for trolley wheels. These might be metal, but maybe not. For an extremely lightweight vehicle, wooden wheels with plastic rims might be sufficient.
An open-source system for setting up rails. Again, these might be metal, but they might also be concrete if the vehicle is light enough. Concrete is a lot easier to buy. Maybe it's a combination of concrete and off-the-shelf metal components. In any case, it should be standard-gauge, since we're trying to bootstrap trolley systems that will eventually work with professionally built streetcars, and the fastest way to do that is to build a stub that can be expanded later.
An open-source design for a handcar. This might be easier to put together in the short term than a full-scale trolley. As with the trolley subproject and the track subproject, this should be standard-gauge.
The trolley itself. This is probably the culmination of the work done during the other three projects. It should still be fairly tiny and lightweight for a trolley, since it will (at least initially) be operating on open-source infrastructure -- i.e., maybe on concrete rails.
Anyhow, as the bullet points make clear, the idea would be to build something primitive and cheap, then gradually upgrade all of the pieces to more professional quality once a proof of concept has been driving around for awhile.